+++ /dev/null
-This is the Bash FAQ, version 3.24, for Bash version 2.05b.
-
-This document contains a set of frequently-asked questions concerning
-Bash, the GNU Bourne-Again Shell. Bash is a freely-available command
-interpreter with advanced features for both interactive use and shell
-programming.
-
-Another good source of basic information about shells is the collection
-of FAQ articles periodically posted to comp.unix.shell.
-
-Questions and comments concerning this document should be sent to
-chet@po.cwru.edu.
-
-This document is available for anonymous FTP with the URL
-
-ftp://ftp.cwru.edu/pub/bash/FAQ
-
-The Bash home page is http://cnswww.cns.cwru.edu/~chet/bash/bashtop.html
-
-----------
-Contents:
-
-Section A: The Basics
-
-A1) What is it?
-A2) What's the latest version?
-A3) Where can I get it?
-A4) On what machines will bash run?
-A5) Will bash run on operating systems other than Unix?
-A6) How can I build bash with gcc?
-A7) How can I make bash my login shell?
-A8) I just changed my login shell to bash, and now I can't FTP into my
- machine. Why not?
-A9) What's the `POSIX 1003.2 standard'?
-A10) What is the bash `posix mode'?
-
-Section B: The latest version
-
-B1) What's new in version 2.05b?
-B2) Are there any user-visible incompatibilities between bash-2.05b and
- bash-1.14.7?
-
-Section C: Differences from other Unix shells
-
-C1) How does bash differ from sh, the Bourne shell?
-C2) How does bash differ from the Korn shell, version ksh88?
-C3) Which new features in ksh-93 are not in bash, and which are?
-
-Section D: Why does bash do some things differently than other Unix shells?
-
-D1) Why does bash run a different version of `command' than
- `which command' says it will?
-D2) Why doesn't bash treat brace expansions exactly like csh?
-D3) Why doesn't bash have csh variable modifiers?
-D4) How can I make my csh aliases work when I convert to bash?
-D5) How can I pipe standard output and standard error from one command to
- another, like csh does with `|&'?
-D6) Now that I've converted from ksh to bash, are there equivalents to
- ksh features like autoloaded functions and the `whence' command?
-
-Section E: Why does bash do certain things the way it does?
-
-E1) Why is the bash builtin `test' slightly different from /bin/test?
-E2) Why does bash sometimes say `Broken pipe'?
-E3) When I have terminal escape sequences in my prompt, why does bash
- wrap lines at the wrong column?
-E4) If I pipe the output of a command into `read variable', why doesn't
- the output show up in $variable when the read command finishes?
-E5) I have a bunch of shell scripts that use backslash-escaped characters
- in arguments to `echo'. Bash doesn't interpret these characters. Why
- not, and how can I make it understand them?
-E6) Why doesn't a while or for loop get suspended when I type ^Z?
-E7) What about empty for loops in Makefiles?
-E8) Why does the arithmetic evaluation code complain about `08'?
-E9) Why does the pattern matching expression [A-Z]* match files beginning
- with every letter except `z'?
-E10) Why does `cd //' leave $PWD as `//'?
-E11) If I resize my xterm while another program is running, why doesn't bash
- notice the change?
-
-Section F: Things to watch out for on certain Unix versions
-
-F1) Why can't I use command line editing in my `cmdtool'?
-F2) I built bash on Solaris 2. Why do globbing expansions and filename
- completion chop off the first few characters of each filename?
-F3) Why does bash dump core after I interrupt username completion or
- `~user' tilde expansion on a machine running NIS?
-F4) I'm running SVR4.2. Why is the line erased every time I type `@'?
-F5) Why does bash report syntax errors when my C News scripts use a
- redirection before a subshell command?
-F6) Why can't I use vi-mode editing on Red Hat Linux 6.1?
-F7) Why do bash-2.05a and bash-2.05b fail to compile `printf.def' on
- HP/UX 11.x?
-
-Section G: How can I get bash to do certain common things?
-
-G1) How can I get bash to read and display eight-bit characters?
-G2) How do I write a function `x' to replace builtin command `x', but
- still invoke the command from within the function?
-G3) How can I find the value of a shell variable whose name is the value
- of another shell variable?
-G4) How can I make the bash `time' reserved word print timing output that
- looks like the output from my system's /usr/bin/time?
-G5) How do I get the current directory into my prompt?
-G6) How can I rename "*.foo" to "*.bar"?
-G7) How can I translate a filename from uppercase to lowercase?
-G8) How can I write a filename expansion (globbing) pattern that will match
- all files in the current directory except "." and ".."?
-
-Section H: Where do I go from here?
-
-H1) How do I report bugs in bash, and where should I look for fixes and
- advice?
-H2) What kind of bash documentation is there?
-H3) What's coming in future versions?
-H4) What's on the bash `wish list'?
-H5) When will the next release appear?
-
-----------
-Section A: The Basics
-
-A1) What is it?
-
-Bash is a Unix command interpreter (shell). It is an implementation of
-the Posix 1003.2 shell standard, and resembles the Korn and System V
-shells.
-
-Bash contains a number of enhancements over those shells, both
-for interactive use and shell programming. Features geared
-toward interactive use include command line editing, command
-history, job control, aliases, and prompt expansion. Programming
-features include additional variable expansions, shell
-arithmetic, and a number of variables and options to control
-shell behavior.
-
-Bash was originally written by Brian Fox of the Free Software
-Foundation. The current developer and maintainer is Chet Ramey
-of Case Western Reserve University.
-
-A2) What's the latest version?
-
-The latest version is 2.05b, first made available on Wednesday, 17
-July, 2002.
-
-A3) Where can I get it?
-
-Bash is the GNU project's shell, and so is available from the
-master GNU archive site, ftp.gnu.org, and its mirrors. The
-latest version is also available for FTP from ftp.cwru.edu.
-The following URLs tell how to get version 2.05b:
-
-ftp://ftp.gnu.org/pub/gnu/bash/bash-2.05b.tar.gz
-ftp://ftp.cwru.edu/pub/bash/bash-2.05b.tar.gz
-
-Formatted versions of the documentation are available with the URLs:
-
-ftp://ftp.gnu.org/pub/gnu/bash/bash-doc-2.05b.tar.gz
-ftp://ftp.cwru.edu/pub/bash/bash-doc-2.05b.tar.gz
-
-A4) On what machines will bash run?
-
-Bash has been ported to nearly every version of UNIX. All you
-should have to do to build it on a machine for which a port
-exists is to type `configure' and then `make'. The build process
-will attempt to discover the version of UNIX you have and tailor
-itself accordingly, using a script created by GNU autoconf.
-
-More information appears in the file `INSTALL' in the distribution.
-
-The Bash web page (http://cnswww.cns.cwru.edu/~chet/bash/bashtop.html)
-explains how to obtain binary versions of bash for most of the major
-commercial Unix systems.
-
-A5) Will bash run on operating systems other than Unix?
-
-Configuration specifics for Unix-like systems such as QNX and
-LynxOS are included in the distribution. Bash-2.05 and later
-versions should compile and run on Minix 2.0 (patches were
-contributed), but I don't believe anyone has built bash-2.x on
-earlier Minix versions yet.
-
-Bash has been ported to versions of Windows implementing the Win32
-programming interface. This includes Windows 95 and Windows NT.
-The port was done by Cygnus Solutions as part of their CYGWIN
-project. For more information about the project, look at the URLs
-
-http://www.cygwin.com/
-http://sourceware.cygnus.com/cygwin
-
-Cygnus originally ported bash-1.14.7, and that port was part of their
-early GNU-Win32 (the original name) releases. Cygnus has also done a
-port of bash-2.05 to the CYGWIN environment, and it is available as
-part of their current release.
-
-Bash-2.05b should require no local Cygnus changes to build and run under
-CYGWIN.
-
-The Cygnus port works only on Intel machines. There is a port of bash
-(I don't know which version) to the alpha/NT environment available from
-
-ftp://ftp.gnustep.org//pub/win32/bash-alpha-nt-1.01.tar.gz
-
-DJ Delorie has a port of bash-2.x which runs under MS-DOS, as part
-of the DJGPP project. For more information on the project, see
-
-http://www.delorie.com/djgpp/
-
-I have been told that the original DJGPP port was done by Daisuke Aoyama.
-
-Mark Elbrecht <snowball3@bigfoot.com> has sent me notice that bash-2.04
-is available for DJGPP V2. The files are available as:
-
-ftp://ftp.simtel.net/pub/simtelnet/gnu/djgpp/v2gnu/bsh204b.zip binary
-ftp://ftp.simtel.net/pub/simtelnet/gnu/djgpp/v2gnu/bsh204d.zip documentation
-ftp://ftp.simtel.net/pub/simtelnet/gnu/djgpp/v2gnu/bsh204s.zip source
-
-Mark has begun to work with bash-2.05, but I don't know the status.
-
-Ports of bash-1.12 and bash-2.0 are available for OS/2 from
-
-ftp://hobbes.nmsu.edu/pub/os2/util/shell/bash_112.zip
-ftp://hobbes.nmsu.edu/pub/os2/util/shell/bash-2.0(253).zip
-
-I haven't looked at either, but the second appears to be a binary-only
-distribution. Beware.
-
-I have received word that Bash (I'm not sure which version, but I
-believe that it's at least bash-2.02.1) is the standard shell on
-BeOS.
-
-A6) How can I build bash with gcc?
-
-Bash configures to use gcc by default if it is available. Read the
-file INSTALL in the distribution for more information.
-
-A7) How can I make bash my login shell?
-
-Some machines let you use `chsh' to change your login shell. Other
-systems use `passwd -s' or `passwd -e'. If one of these works for
-you, that's all you need. Note that many systems require the full
-pathname to a shell to appear in /etc/shells before you can make it
-your login shell. For this, you may need the assistance of your
-friendly local system administrator.
-
-If you cannot do this, you can still use bash as your login shell, but
-you need to perform some tricks. The basic idea is to add a command
-to your login shell's startup file to replace your login shell with
-bash.
-
-For example, if your login shell is csh or tcsh, and you have installed
-bash in /usr/gnu/bin/bash, add the following line to ~/.login:
-
- if ( -f /usr/gnu/bin/bash ) exec /usr/gnu/bin/bash --login
-
-(the `--login' tells bash that it is a login shell).
-
-It's not a good idea to put this command into ~/.cshrc, because every
-csh you run without the `-f' option, even ones started to run csh scripts,
-reads that file. If you must put the command in ~/.cshrc, use something
-like
-
- if ( $?prompt ) exec /usr/gnu/bin/bash --login
-
-to ensure that bash is exec'd only when the csh is interactive.
-
-If your login shell is sh or ksh, you have to do two things.
-
-First, create an empty file in your home directory named `.bash_profile'.
-The existence of this file will prevent the exec'd bash from trying to
-read ~/.profile, and re-execing itself over and over again. ~/.bash_profile
-is the first file bash tries to read initialization commands from when
-it is invoked as a login shell.
-
-Next, add a line similar to the above to ~/.profile:
-
- [ -f /usr/gnu/bin/bash ] && [ -x /usr/gnu/bin/bash ] && \
- exec /usr/gnu/bin/bash --login
-
-This will cause login shells to replace themselves with bash running as
-a login shell. Once you have this working, you can copy your initialization
-code from ~/.profile to ~/.bash_profile.
-
-I have received word that the recipe supplied above is insufficient for
-machines running CDE. CDE has a maze of twisty little startup files, all
-slightly different.
-
-If you cannot change your login shell in the password file to bash, you
-will have to (apparently) live with CDE using the shell in the password
-file to run its startup scripts. If you have changed your shell to bash,
-there is code in the CDE startup files (on Solaris, at least) that attempts
-to do the right thing. It is, however, often broken, and may require that
-you use the $BASH_ENV trick described below.
-
-`dtterm' claims to use $SHELL as the default program to start, so if you
-can change $SHELL in the CDE startup files, you should be able to use bash
-in your terminal windows.
-
-Setting DTSOURCEPROFILE in ~/.dtprofile will cause the `Xsession' program
-to read your login shell's startup files. You may be able to use bash for
-the rest of the CDE programs by setting SHELL to bash in ~/.dtprofile as
-well, but I have not tried this.
-
-You can use the above `exec' recipe to start bash when not logging in with
-CDE by testing the value of the DT variable:
-
- if [ -n "$DT" ]; then
- [ -f /usr/gnu/bin/bash ] && exec /usr/gnu/bin/bash --login
- fi
-
-If CDE starts its shells non-interactively during login, the login shell
-startup files (~/.profile, ~/.bash_profile) will not be sourced at login.
-To get around this problem, append a line similar to the following to your
-~/.dtprofile:
-
- BASH_ENV=${HOME}/.bash_profile ; export BASH_ENV
-
-and add the following line to the beginning of ~/.bash_profile:
-
- unset BASH_ENV
-
-A8) I just changed my login shell to bash, and now I can't FTP into my
- machine. Why not?
-
-You must add the full pathname to bash to the file /etc/shells. As
-noted in the answer to the previous question, many systems require
-this before you can make bash your login shell.
-
-Most versions of ftpd use this file to prohibit `special' users
-such as `uucp' and `news' from using FTP.
-
-A9) What's the `POSIX 1003.2 standard'?
-
-POSIX is a name originally coined by Richard Stallman for a
-family of open system standards based on UNIX. There are a
-number of aspects of UNIX under consideration for
-standardization, from the basic system services at the system
-call and C library level to applications and tools to system
-administration and management. Each area of standardization is
-assigned to a working group in the 1003 series.
-
-The POSIX Shell and Utilities standard has been developed by IEEE
-Working Group 1003.2 (POSIX.2). It concentrates on the command
-interpreter interface and utility programs commonly executed from
-the command line or by other programs. An initial version of the
-standard has been approved and published by the IEEE, and work is
-currently underway to update it.
-
-Bash is concerned with the aspects of the shell's behavior
-defined by POSIX.2. The shell command language has of course
-been standardized, including the basic flow control and program
-execution constructs, I/O redirection and pipelining, argument
-handling, variable expansion, and quoting.
-
-The `special' builtins, which must be implemented as part of the
-shell to provide the desired functionality, are specified as
-being part of the shell; examples of these are `eval' and
-`export'. Other utilities appear in the sections of POSIX.2 not
-devoted to the shell which are commonly (and in some cases must
-be) implemented as builtin commands, such as `read' and `test'.
-POSIX.2 also specifies aspects of the shell's interactive
-behavior as part of the UPE, including job control and command
-line editing. Only vi-style line editing commands have been
-standardized; emacs editing commands were left out due to
-objections.
-
-The Open Group has made an older version of its Single Unix
-Specification (version 2), which is very similar to POSIX.2,
-available on the web at
-
-http://www.opengroup.org/onlinepubs/007908799/
-
-The Single Unix Specification, version 3, is available on the web at
-
-http://www.opengroup.org/onlinepubs/007904975/
-
-A10) What is the bash `posix mode'?
-
-Although bash is an implementation of the POSIX.2 shell
-specification, there are areas where the bash default behavior
-differs from that spec. The bash `posix mode' changes the bash
-behavior in these areas so that it obeys the spec more closely.
-
-Posix mode is entered by starting bash with the --posix or
-'-o posix' option or executing `set -o posix' after bash is running.
-
-The specific aspects of bash which change when posix mode is
-active are listed in the file POSIX in the bash distribution.
-They are also listed in a section in the Bash Reference Manual
-(from which that file is generated).
-
-Section B: The latest version
-
-B1) What's new in version 2.05b?
-
-The raison d'etre for bash-2.05b is to make a second intermediate
-release containing the first of the new features to be available
-in bash-3.0 and get feedback on those features before proceeding.
-The major new feature is multibyte character support in both Bash
-and Readline.
-
-Bash-2.05b contains the following new features (see the manual page for
-complete descriptions and the CHANGES and NEWS files in the bash-2.05b
-distribution):
-
-o support for multibyte characters has been added to both bash and readline
-
-o the DEBUG trap is now run *before* simple commands, ((...)) commands,
- [[...]] conditional commands, and for ((...)) loops
-
-o the shell now performs arithmetic in the largest integer size the machine
- supports (intmax_t)
-
-o there is a new \D{...} prompt expansion; passes the `...' to strftime(3)
- and inserts the result into the expanded prompt
-
-o there is a new `here-string' redirection operator: <<< word
-
-o when displaying variables, function attributes and definitions are shown
- separately, allowing them to be re-used as input (attempting to re-use
- the old output would result in syntax errors).
-
-o `read' has a new `-u fd' option to read from a specified file descriptor
-
-o the bash debugger in examples/bashdb has been modified to work with the
- new DEBUG trap semantics, the command set has been made more gdb-like,
- and the changes to $LINENO make debugging functions work better
-
-o the expansion of $LINENO inside a shell function is only relative to the
- function start if the shell is interactive -- if the shell is running a
- script, $LINENO expands to the line number in the script. This is as
- POSIX-2001 requires
-
-
-A short feature history dating from Bash-2.0:
-
-Bash-2.05a introduced the following new features:
-
-o The `printf' builtin has undergone major work
-
-o There is a new read-only `shopt' option: login_shell, which is set by
- login shells and unset otherwise
-
-o New `\A' prompt string escape sequence; expanding to time in 24-hour
- HH:MM format
-
-o New `-A group/-g' option to complete and compgen; goes group name
- completion
-
-o New [+-]O invocation option to set and unset `shopt' options at startup
-
-o ksh-like `ERR' trap
-
-o `for' loops now allow empty word lists after the `in' reserved word
-
-o new `hard' and `soft' arguments for the `ulimit' builtin
-
-o Readline can be configured to place the user at the same point on the line
- when retrieving commands from the history list
-
-o Readline can be configured to skip `hidden' files (filenames with a leading
- `.' on Unix) when performing completion
-
-Bash-2.05 introduced the following new features:
-
-o This version has once again reverted to using locales and strcoll(3) when
- processing pattern matching bracket expressions, as POSIX requires.
-o Added a new `--init-file' invocation argument as a synonym for `--rcfile',
- per the new GNU coding standards.
-o The /dev/tcp and /dev/udp redirections now accept service names as well as
- port numbers.
-o `complete' and `compgen' now take a `-o value' option, which controls some
- of the aspects of that compspec. Valid values are:
-
- default - perform bash default completion if programmable
- completion produces no matches
- dirnames - perform directory name completion if programmable
- completion produces no matches
- filenames - tell readline that the compspec produces filenames,
- so it can do things like append slashes to
- directory names and suppress trailing spaces
-o A new loadable builtin, realpath, which canonicalizes and expands symlinks
- in pathname arguments.
-o When `set' is called without options, it prints function defintions in a
- way that allows them to be reused as input. This affects `declare' and
- `declare -p' as well. This only happens when the shell is not in POSIX
- mode, since POSIX.2 forbids this behavior.
-
-Bash-2.04 introduced the following new features:
-
-o Programmable word completion with the new `complete' and `compgen' builtins;
- examples are provided in examples/complete/complete-examples
-o `history' has a new `-d' option to delete a history entry
-o `bind' has a new `-x' option to bind key sequences to shell commands
-o The prompt expansion code has new `\j' and `\l' escape sequences
-o The `no_empty_cmd_completion' shell option, if enabled, inhibits
- command completion when TAB is typed on an empty line
-o `help' has a new `-s' option to print a usage synopsis
-o New arithmetic operators: var++, var--, ++var, --var, expr1,expr2 (comma)
-o New ksh93-style arithmetic for command:
- for ((expr1 ; expr2; expr3 )); do list; done
-o `read' has new options: `-t', `-n', `-d', `-s'
-o The redirection code handles several filenames specially: /dev/fd/N,
- /dev/stdin, /dev/stdout, /dev/stderr
-o The redirection code now recognizes /dev/tcp/HOST/PORT and
- /dev/udp/HOST/PORT and tries to open a TCP or UDP socket, respectively,
- to the specified port on the specified host
-o The ${!prefix*} expansion has been implemented
-o A new FUNCNAME variable, which expands to the name of a currently-executing
- function
-o The GROUPS variable is no longer readonly
-o A new shopt `xpg_echo' variable, to control the behavior of echo with
- respect to backslash-escape sequences at runtime
-o The NON_INTERACTIVE_LOGIN_SHELLS #define has returned
-
-The version of Readline released with Bash-2.04, Readline-4.1, had several
-new features as well:
-
-o Parentheses matching is always compiled into readline, and controllable
- with the new `blink-matching-paren' variable
-o The history-search-forward and history-search-backward functions now leave
- point at the end of the line when the search string is empty, like
- reverse-search-history, and forward-search-history
-o A new function for applications: rl_on_new_line_with_prompt()
-o New variables for applications: rl_already_prompted, and rl_gnu_readline_p
-
-
-Bash-2.03 had very few new features, in keeping with the convention
-that odd-numbered releases provide mainly bug fixes. A number of new
-features were added to Readline, mostly at the request of the Cygnus
-folks.
-
-A new shopt option, `restricted_shell', so that startup files can test
- whether or not the shell was started in restricted mode
-Filename generation is now performed on the words between ( and ) in
- compound array assignments (this is really a bug fix)
-OLDPWD is now auto-exported, as POSIX.2 requires
-ENV and BASH_ENV are read-only variables in a restricted shell
-Bash may now be linked against an already-installed Readline library,
- as long as the Readline library is version 4 or newer
-All shells begun with the `--login' option will source the login shell
- startup files, even if the shell is not interactive
-
-There were lots of changes to the version of the Readline library released
-along with Bash-2.03. For a complete list of the changes, read the file
-CHANGES in the Bash-2.03 distribution.
-
-Bash-2.02 contained the following new features:
-
-a new version of malloc (based on the old GNU malloc code in previous
- bash versions) that is more page-oriented, more conservative
- with memory usage, does not `orphan' large blocks when they
- are freed, is usable on 64-bit machines, and has allocation
- checking turned on unconditionally
-POSIX.2-style globbing character classes ([:alpha:], [:alnum:], etc.)
-POSIX.2-style globbing equivalence classes
-POSIX.2-style globbing collating symbols
-the ksh [[...]] extended conditional command
-the ksh egrep-style extended pattern matching operators
-a new `printf' builtin
-the ksh-like $(<filename) command substitution, which is equivalent to
- $(cat filename)
-new tilde prefixes that expand to directories from the directory stack
-new `**' arithmetic operator to do exponentiation
-case-insensitive globbing (filename expansion)
-menu completion a la tcsh
-`magic-space' history expansion function like tcsh
-the readline inputrc `language' has a new file inclusion directive ($include)
-
-Bash-2.01 contained only a few new features:
-
-new `GROUPS' builtin array variable containing the user's group list
-new bindable readline commands: history-and-alias-expand-line and
- alias-expand-line
-
-Bash-2.0 contained extensive changes and new features from bash-1.14.7.
-Here's a short list:
-
-new `time' reserved word to time pipelines, shell builtins, and
- shell functions
-one-dimensional arrays with a new compound assignment statement,
- appropriate expansion constructs and modifications to some
- of the builtins (read, declare, etc.) to use them
-new quoting syntaxes for ANSI-C string expansion and locale-specific
- string translation
-new expansions to do substring extraction, pattern replacement, and
- indirect variable expansion
-new builtins: `disown' and `shopt'
-new variables: HISTIGNORE, SHELLOPTS, PIPESTATUS, DIRSTACK, GLOBIGNORE,
- MACHTYPE, BASH_VERSINFO
-special handling of many unused or redundant variables removed
- (e.g., $notify, $glob_dot_filenames, $no_exit_on_failed_exec)
-dynamic loading of new builtin commands; many loadable examples provided
-new prompt expansions: \a, \e, \n, \H, \T, \@, \v, \V
-history and aliases available in shell scripts
-new readline variables: enable-keypad, mark-directories, input-meta,
- visible-stats, disable-completion, comment-begin
-new readline commands to manipulate the mark and operate on the region
-new readline emacs mode commands and bindings for ksh-88 compatibility
-updated and extended builtins
-new DEBUG trap
-expanded (and now documented) restricted shell mode
-
-implementation stuff:
-autoconf-based configuration
-nearly all of the bugs reported since version 1.14 have been fixed
-most builtins converted to use builtin `getopt' for consistency
-most builtins use -p option to display output in a reusable form
- (for consistency)
-grammar tighter and smaller (66 reduce-reduce conflicts gone)
-lots of code now smaller and faster
-test suite greatly expanded
-
-B2) Are there any user-visible incompatibilities between bash-2.05b and
- bash-1.14.7?
-
-There are a few incompatibilities between version 1.14.7 and version 2.05b.
-They are detailed in the file COMPAT in the bash distribution. That file
-is not meant to be all-encompassing; send mail to bash-maintainers@gnu.org
-if if you find something that's not mentioned there.
-
-Section C: Differences from other Unix shells
-
-C1) How does bash differ from sh, the Bourne shell?
-
-This is a non-comprehensive list of features that differentiate bash
-from the SVR4.2 shell. The bash manual page explains these more
-completely.
-
-Things bash has that sh does not:
- long invocation options
- [+-]O invocation option
- -l invocation option
- `!' reserved word to invert pipeline return value
- `time' reserved word to time pipelines and shell builtins
- the `function' reserved word
- the `select' compound command and reserved word
- arithmetic for command: for ((expr1 ; expr2; expr3 )); do list; done
- new $'...' and $"..." quoting
- the $(...) form of command substitution
- the $(<filename) form of command substitution, equivalent to
- $(cat filename)
- the ${#param} parameter value length operator
- the ${!param} indirect parameter expansion operator
- the ${!param*} prefix expansion operator
- the ${param:offset[:length]} parameter substring operator
- the ${param/pat[/string]} parameter pattern substitution operator
- expansions to perform substring removal (${p%[%]w}, ${p#[#]w})
- expansion of positional parameters beyond $9 with ${num}
- variables: BASH, BASH_VERSION, BASH_VERSINFO, UID, EUID, REPLY,
- TIMEFORMAT, PPID, PWD, OLDPWD, SHLVL, RANDOM, SECONDS,
- LINENO, HISTCMD, HOSTTYPE, OSTYPE, MACHTYPE, HOSTNAME,
- ENV, PS3, PS4, DIRSTACK, PIPESTATUS, HISTSIZE, HISTFILE,
- HISTFILESIZE, HISTCONTROL, HISTIGNORE, GLOBIGNORE, GROUPS,
- PROMPT_COMMAND, FCEDIT, FIGNORE, IGNOREEOF, INPUTRC,
- SHELLOPTS, OPTERR, HOSTFILE, TMOUT, FUNCNAME, histchars,
- auto_resume
- DEBUG trap
- ERR trap
- variable arrays with new compound assignment syntax
- redirections: <>, &>, >|, <<<, [n]<&word-, [n]>&word-
- prompt string special char translation and variable expansion
- auto-export of variables in initial environment
- command search finds functions before builtins
- bash return builtin will exit a file sourced with `.'
- builtins: cd -/-L/-P, exec -l/-c/-a, echo -e/-E, hash -d/-l/-p/-t.
- export -n/-f/-p/name=value, pwd -L/-P,
- read -e/-p/-a/-t/-n/-d/-s/-u,
- readonly -a/-f/name=value, trap -l, set +o,
- set -b/-m/-o option/-h/-p/-B/-C/-H/-P,
- unset -f/-v, ulimit -m/-p/-u,
- type -a/-p/-t/-f/-P, suspend -f, kill -n,
- test -o optname/s1 == s2/s1 < s2/s1 > s2/-nt/-ot/-ef/-O/-G/-S
- bash reads ~/.bashrc for interactive shells, $ENV for non-interactive
- bash restricted shell mode is more extensive
- bash allows functions and variables with the same name
- brace expansion
- tilde expansion
- arithmetic expansion with $((...)) and `let' builtin
- the `[[...]]' extended conditional command
- process substitution
- aliases and alias/unalias builtins
- local variables in functions and `local' builtin
- readline and command-line editing with programmable completion
- command history and history/fc builtins
- csh-like history expansion
- other new bash builtins: bind, command, compgen, complete, builtin,
- declare/typeset, dirs, enable, fc, help,
- history, logout, popd, pushd, disown, shopt,
- printf
- exported functions
- filename generation when using output redirection (command >a*)
- POSIX.2-style globbing character classes
- POSIX.2-style globbing equivalence classes
- POSIX.2-style globbing collating symbols
- egrep-like extended pattern matching operators
- case-insensitive pattern matching and globbing
- variable assignments preceding commands affect only that command,
- even for builtins and functions
- posix mode
- redirection to /dev/fd/N, /dev/stdin, /dev/stdout, /dev/stderr,
- /dev/tcp/host/port, /dev/udp/host/port
-
-Things sh has that bash does not:
- uses variable SHACCT to do shell accounting
- includes `stop' builtin (bash can use alias stop='kill -s STOP')
- `newgrp' builtin
- turns on job control if called as `jsh'
- $TIMEOUT (like bash $TMOUT)
- `^' is a synonym for `|'
- new SVR4.2 sh builtins: mldmode, priv
-
-Implementation differences:
- redirection to/from compound commands causes sh to create a subshell
- bash does not allow unbalanced quotes; sh silently inserts them at EOF
- bash does not mess with signal 11
- sh sets (euid, egid) to (uid, gid) if -p not supplied and uid < 100
- bash splits only the results of expansions on IFS, using POSIX.2
- field splitting rules; sh splits all words on IFS
- sh does not allow MAILCHECK to be unset (?)
- sh does not allow traps on SIGALRM or SIGCHLD
- bash allows multiple option arguments when invoked (e.g. -x -v);
- sh allows only a single option argument (`sh -x -v' attempts
- to open a file named `-v', and, on SunOS 4.1.4, dumps core.
- On Solaris 2.4 and earlier versions, sh goes into an infinite
- loop.)
- sh exits a script if any builtin fails; bash exits only if one of
- the POSIX.2 `special' builtins fails
-
-C2) How does bash differ from the Korn shell, version ksh88?
-
-Things bash has or uses that ksh88 does not:
- long invocation options
- [-+]O invocation option
- -l invocation option
- `!' reserved word
- arithmetic for command: for ((expr1 ; expr2; expr3 )); do list; done
- arithmetic in largest machine-supported size (intmax_t)
- posix mode and posix conformance
- command hashing
- tilde expansion for assignment statements that look like $PATH
- process substitution with named pipes if /dev/fd is not available
- the ${!param} indirect parameter expansion operator
- the ${!param*} prefix expansion operator
- the ${param:offset[:length]} parameter substring operator
- the ${param/pat[/string]} parameter pattern substitution operator
- variables: BASH, BASH_VERSION, BASH_VERSINFO, UID, EUID, SHLVL,
- TIMEFORMAT, HISTCMD, HOSTTYPE, OSTYPE, MACHTYPE,
- HISTFILESIZE, HISTIGNORE, HISTCONTROL, PROMPT_COMMAND,
- IGNOREEOF, FIGNORE, INPUTRC, HOSTFILE, DIRSTACK,
- PIPESTATUS, HOSTNAME, OPTERR, SHELLOPTS, GLOBIGNORE,
- GROUPS, FUNCNAME, histchars, auto_resume
- prompt expansion with backslash escapes and command substitution
- redirection: &> (stdout and stderr), <<<, [n]<&word-, [n]>&word-
- more extensive and extensible editing and programmable completion
- builtins: bind, builtin, command, declare, dirs, echo -e/-E, enable,
- exec -l/-c/-a, fc -s, export -n/-f/-p, hash, help, history,
- jobs -x/-r/-s, kill -s/-n/-l, local, logout, popd, pushd,
- read -e/-p/-a/-t/-n/-d/-s, readonly -a/-n/-f/-p,
- set -o braceexpand/-o histexpand/-o interactive-comments/
- -o notify/-o physical/-o posix/-o hashall/-o onecmd/
- -h/-B/-C/-b/-H/-P, set +o, suspend, trap -l, type,
- typeset -a/-F/-p, ulimit -u, umask -S, alias -p, shopt,
- disown, printf, complete, compgen
- `!' csh-style history expansion
- POSIX.2-style globbing character classes
- POSIX.2-style globbing equivalence classes
- POSIX.2-style globbing collating symbols
- egrep-like extended pattern matching operators
- case-insensitive pattern matching and globbing
- `**' arithmetic operator to do exponentiation
- redirection to /dev/fd/N, /dev/stdin, /dev/stdout, /dev/stderr
- arrays of unlimited size
- TMOUT is default timeout for `read' and `select'
-
-Things ksh88 has or uses that bash does not:
- tracked aliases (alias -t)
- variables: ERRNO, FPATH, EDITOR, VISUAL
- co-processes (|&, >&p, <&p)
- weirdly-scoped functions
- typeset +f to list all function names without definitions
- text of command history kept in a file, not memory
- builtins: alias -x, cd old new, fc -e -, newgrp, print,
- read -p/-s/var?prompt, set -A/-o gmacs/
- -o bgnice/-o markdirs/-o nolog/-o trackall/-o viraw/-s,
- typeset -H/-L/-R/-Z/-A/-ft/-fu/-fx/-l/-u/-t, whence
- using environment to pass attributes of exported variables
- arithmetic evaluation done on arguments to some builtins
- reads .profile from $PWD when invoked as login shell
-
-Implementation differences:
- ksh runs last command of a pipeline in parent shell context
- bash has brace expansion by default (ksh88 compile-time option)
- bash has fixed startup file for all interactive shells; ksh reads $ENV
- bash has exported functions
- bash command search finds functions before builtins
- bash waits for all commands in pipeline to exit before returning status
- emacs-mode editing has some slightly different key bindings
-
-C3) Which new features in ksh-93 are not in bash, and which are?
-
-New things in ksh-93 not in bash-2.05b:
- associative arrays
- floating point arithmetic and variables
- math library functions
- ${!name[sub]} name of subscript for associative array
- `.' is allowed in variable names to create a hierarchical namespace
- more extensive compound assignment syntax
- discipline functions
- `sleep' and `getconf' builtins (bash has loadable versions)
- typeset -n and `nameref' variables
- KEYBD trap
- variables: .sh.edchar, .sh.edmode, .sh.edcol, .sh.edtext, .sh.version,
- .sh.name, .sh.subscript, .sh.value, .sh.match, HISTEDIT
- backreferences in pattern matching (\N)
- `&' operator in pattern lists for matching
- print -f (bash uses printf)
- `fc' has been renamed to `hist'
- `.' can execute shell functions
- exit statuses between 0 and 255
- set -o pipefail
- `+=' variable assignment operator
- FPATH and PATH mixing
- getopts -a
- -I invocation option
- DEBUG trap now executed before each simple command, instead of after
- printf %H, %P, %T, %Z modifiers, output base for %d
- lexical scoping for local variables in `ksh' functions
- no scoping for local variables in `POSIX' functions
-
-New things in ksh-93 present in bash-2.05b:
- [n]<&word- and [n]>&word- redirections (combination dup and close)
- for (( expr1; expr2; expr3 )) ; do list; done - arithmetic for command
- ?:, ++, --, `expr1 , expr2' arithmetic operators
- expansions: ${!param}, ${param:offset[:len]}, ${param/pat[/str]},
- ${!param*}
- compound array assignment
- the `!' reserved word
- loadable builtins -- but ksh uses `builtin' while bash uses `enable'
- `command', `builtin', `disown' builtins
- new $'...' and $"..." quoting
- FIGNORE (but bash uses GLOBIGNORE), HISTCMD
- set -o notify/-C
- changes to kill builtin
- read -A (bash uses read -a)
- read -t/-d
- trap -p
- exec -c/-a
- `.' restores the positional parameters when it completes
- POSIX.2 `test'
- umask -S
- unalias -a
- command and arithmetic substitution performed on PS1, PS4, and ENV
- command name completion
- ENV processed only for interactive shells
-
-Section D: Why does bash do some things differently than other Unix shells?
-
-D1) Why does bash run a different version of `command' than
- `which command' says it will?
-
-On many systems, `which' is actually a csh script that assumes
-you're running csh. In tcsh, `which' and its cousin `where'
-are builtins. On other Unix systems, `which' is a perl script
-that uses the PATH environment variable.
-
-The csh script version reads the csh startup files from your
-home directory and uses those to determine which `command' will
-be invoked. Since bash doesn't use any of those startup files,
-there's a good chance that your bash environment differs from
-your csh environment. The bash `type' builtin does everything
-`which' does, and will report correct results for the running
-shell. If you're really wedded to the name `which', try adding
-the following function definition to your .bashrc:
-
- which()
- {
- builtin type "$@"
- }
-
-If you're moving from tcsh and would like to bring `where' along
-as well, use this function:
-
- where()
- {
- builtin type -a "$@"
- }
-
-D2) Why doesn't bash treat brace expansions exactly like csh?
-
-The only difference between bash and csh brace expansion is that
-bash requires a brace expression to contain at least one unquoted
-comma if it is to be expanded. Any brace-surrounded word not
-containing an unquoted comma is left unchanged by the brace
-expansion code. This affords the greatest degree of sh
-compatibility.
-
-Bash, ksh, zsh, and pd-ksh all implement brace expansion this way.
-
-D3) Why doesn't bash have csh variable modifiers?
-
-Posix has specified a more powerful, albeit somewhat more cryptic,
-mechanism cribbed from ksh, and bash implements it.
-
-${parameter%word}
- Remove smallest suffix pattern. The WORD is expanded to produce
- a pattern. It then expands to the value of PARAMETER, with the
- smallest portion of the suffix matched by the pattern deleted.
-
- x=file.c
- echo ${x%.c}.o
- -->file.o
-
-${parameter%%word}
-
- Remove largest suffix pattern. The WORD is expanded to produce
- a pattern. It then expands to the value of PARAMETER, with the
- largest portion of the suffix matched by the pattern deleted.
-
- x=posix/src/std
- echo ${x%%/*}
- -->posix
-
-${parameter#word}
- Remove smallest prefix pattern. The WORD is expanded to produce
- a pattern. It then expands to the value of PARAMETER, with the
- smallest portion of the prefix matched by the pattern deleted.
-
- x=$HOME/src/cmd
- echo ${x#$HOME}
- -->/src/cmd
-
-${parameter##word}
- Remove largest prefix pattern. The WORD is expanded to produce
- a pattern. It then expands to the value of PARAMETER, with the
- largest portion of the prefix matched by the pattern deleted.
-
- x=/one/two/three
- echo ${x##*/}
- -->three
-
-
-Given
- a=/a/b/c/d
- b=b.xxx
-
- csh bash result
- --- ---- ------
- $a:h ${a%/*} /a/b/c
- $a:t ${a##*/} d
- $b:r ${b%.*} b
- $b:e ${b##*.} xxx
-
-
-D4) How can I make my csh aliases work when I convert to bash?
-
-Bash uses a different syntax to support aliases than csh does.
-The details can be found in the documentation. We have provided
-a shell script which does most of the work of conversion for you;
-this script can be found in ./examples/misc/aliasconv.sh. Here is
-how you use it:
-
-Start csh in the normal way for you. (e.g., `csh')
-
-Pipe the output of `alias' through `aliasconv.sh', saving the
-results into `bash_aliases':
-
- alias | bash aliasconv.sh >bash_aliases
-
-Edit `bash_aliases', carefully reading through any created
-functions. You will need to change the names of some csh specific
-variables to the bash equivalents. The script converts $cwd to
-$PWD, $term to $TERM, $home to $HOME, $user to $USER, and $prompt
-to $PS1. You may also have to add quotes to avoid unwanted
-expansion.
-
-For example, the csh alias:
-
- alias cd 'cd \!*; echo $cwd'
-
-is converted to the bash function:
-
- cd () { command cd "$@"; echo $PWD ; }
-
-The only thing that needs to be done is to quote $PWD:
-
- cd () { command cd "$@"; echo "$PWD" ; }
-
-Merge the edited file into your ~/.bashrc.
-
-There is an additional, more ambitious, script in
-examples/misc/cshtobash that attempts to convert your entire csh
-environment to its bash equivalent. This script can be run as
-simply `cshtobash' to convert your normal interactive
-environment, or as `cshtobash ~/.login' to convert your login
-environment.
-
-D5) How can I pipe standard output and standard error from one command to
- another, like csh does with `|&'?
-
-Use
- command 2>&1 | command2
-
-The key is to remember that piping is performed before redirection, so
-file descriptor 1 points to the pipe when it is duplicated onto file
-descriptor 2.
-
-D6) Now that I've converted from ksh to bash, are there equivalents to
- ksh features like autoloaded functions and the `whence' command?
-
-There are features in ksh-88 and ksh-93 that do not have direct bash
-equivalents. Most, however, can be emulated with very little trouble.
-
-ksh-88 feature Bash equivalent
--------------- ---------------
-compiled-in aliases set up aliases in .bashrc; some ksh aliases are
- bash builtins (hash, history, type)
-coprocesses named pipe pairs (one for read, one for write)
-typeset +f declare -F
-cd, print, whence function substitutes in examples/functions/kshenv
-autoloaded functions examples/functions/autoload is the same as typeset -fu
-read var?prompt read -p prompt var
-
-ksh-93 feature Bash equivalent
--------------- ---------------
-sleep, getconf Bash has loadable versions in examples/loadables
-${.sh.version} $BASH_VERSION
-print -f printf
-hist alias hist=fc
-$HISTEDIT $FCEDIT
-
-Section E: How can I get bash to do certain things, and why does bash do
- things the way it does?
-
-E1) Why is the bash builtin `test' slightly different from /bin/test?
-
-The specific example used here is [ ! x -o x ], which is false.
-
-Bash's builtin `test' implements the Posix.2 spec, which can be
-summarized as follows (the wording is due to David Korn):
-
-Here is the set of rules for processing test arguments.
-
- 0 Args: False
- 1 Arg: True iff argument is not null.
- 2 Args: If first arg is !, True iff second argument is null.
- If first argument is unary, then true if unary test is true
- Otherwise error.
- 3 Args: If second argument is a binary operator, do binary test of $1 $3
- If first argument is !, negate two argument test of $2 $3
- If first argument is `(' and third argument is `)', do the
- one-argument test of the second argument.
- Otherwise error.
- 4 Args: If first argument is !, negate three argument test of $2 $3 $4.
- Otherwise unspecified
- 5 or more Args: unspecified. (Historical shells would use their
- current algorithm).
-
-The operators -a and -o are considered binary operators for the purpose
-of the 3 Arg case.
-
-As you can see, the test becomes (not (x or x)), which is false.
-
-E2) Why does bash sometimes say `Broken pipe'?
-
-If a sequence of commands appears in a pipeline, and one of the
-reading commands finishes before the writer has finished, the
-writer receives a SIGPIPE signal. Many other shells special-case
-SIGPIPE as an exit status in the pipeline and do not report it.
-For example, in:
-
- ps -aux | head
-
-`head' can finish before `ps' writes all of its output, and ps
-will try to write on a pipe without a reader. In that case, bash
-will print `Broken pipe' to stderr when ps is killed by a
-SIGPIPE.
-
-You can build a version of bash that will not report SIGPIPE errors
-by uncommenting the definition of DONT_REPORT_SIGPIPE in the file
-config-top.h.
-
-E3) When I have terminal escape sequences in my prompt, why does bash
- wrap lines at the wrong column?
-
-Readline, the line editing library that bash uses, does not know
-that the terminal escape sequences do not take up space on the
-screen. The redisplay code assumes, unless told otherwise, that
-each character in the prompt is a `printable' character that
-takes up one character position on the screen.
-
-You can use the bash prompt expansion facility (see the PROMPTING
-section in the manual page) to tell readline that sequences of
-characters in the prompt strings take up no screen space.
-
-Use the \[ escape to begin a sequence of non-printing characters,
-and the \] escape to signal the end of such a sequence.
-
-E4) If I pipe the output of a command into `read variable', why doesn't
- the output show up in $variable when the read command finishes?
-
-This has to do with the parent-child relationship between Unix
-processes. It affects all commands run in pipelines, not just
-simple calls to `read'. For example, piping a command's output
-into a `while' loop that repeatedly calls `read' will result in
-the same behavior.
-
-Each element of a pipeline runs in a separate process, a child of
-the shell running the pipeline. A subprocess cannot affect its
-parent's environment. When the `read' command sets the variable
-to the input, that variable is set only in the subshell, not the
-parent shell. When the subshell exits, the value of the variable
-is lost.
-
-Many pipelines that end with `read variable' can be converted
-into command substitutions, which will capture the output of
-a specified command. The output can then be assigned to a
-variable:
-
- grep ^gnu /usr/lib/news/active | wc -l | read ngroup
-
-can be converted into
-
- ngroup=$(grep ^gnu /usr/lib/news/active | wc -l)
-
-This does not, unfortunately, work to split the text among
-multiple variables, as read does when given multiple variable
-arguments. If you need to do this, you can either use the
-command substitution above to read the output into a variable
-and chop up the variable using the bash pattern removal
-expansion operators or use some variant of the following
-approach.
-
-Say /usr/local/bin/ipaddr is the following shell script:
-
-#! /bin/sh
-host `hostname` | awk '/address/ {print $NF}'
-
-Instead of using
-
- /usr/local/bin/ipaddr | read A B C D
-
-to break the local machine's IP address into separate octets, use
-
- OIFS="$IFS"
- IFS=.
- set -- $(/usr/local/bin/ipaddr)
- IFS="$OIFS"
- A="$1" B="$2" C="$3" D="$4"
-
-Beware, however, that this will change the shell's positional
-parameters. If you need them, you should save them before doing
-this.
-
-This is the general approach -- in most cases you will not need to
-set $IFS to a different value.
-
-Some other user-supplied alternatives include:
-
-read A B C D << HERE
- $(IFS=.; echo $(/usr/local/bin/ipaddr))
-HERE
-
-and, where process substitution is available,
-
-read A B C D < <(IFS=.; echo $(/usr/local/bin/ipaddr))
-
-E5) I have a bunch of shell scripts that use backslash-escaped characters
- in arguments to `echo'. Bash doesn't interpret these characters. Why
- not, and how can I make it understand them?
-
-This is the behavior of echo on most Unix System V machines.
-
-The bash builtin `echo' is modeled after the 9th Edition
-Research Unix version of `echo'. It does not interpret
-backslash-escaped characters in its argument strings by default;
-it requires the use of the -e option to enable the
-interpretation. The System V echo provides no way to disable the
-special characters; the bash echo has a -E option to disable
-them.
-
-There is a configuration option that will make bash behave like
-the System V echo and interpret things like `\t' by default. Run
-configure with the --enable-xpg-echo-default option to turn this
-on. Be aware that this will cause some of the tests run when you
-type `make tests' to fail.
-
-There is a shell option, `xpg_echo', settable with `shopt', that will
-change the behavior of echo at runtime. Enabling this option turns
-on expansion of backslash-escape sequences.
-
-E6) Why doesn't a while or for loop get suspended when I type ^Z?
-
-This is a consequence of how job control works on Unix. The only
-thing that can be suspended is the process group. This is a single
-command or pipeline of commands that the shell forks and executes.
-
-When you run a while or for loop, the only thing that the shell forks
-and executes are any commands in the while loop test and commands in
-the loop bodies. These, therefore, are the only things that can be
-suspended when you type ^Z.
-
-If you want to be able to stop the entire loop, you need to put it
-within parentheses, which will force the loop into a subshell that
-may be stopped (and subsequently restarted) as a single unit.
-
-E7) What about empty for loops in Makefiles?
-
-It's fairly common to see constructs like this in automatically-generated
-Makefiles:
-
-SUBDIRS = @SUBDIRS@
-
- ...
-
-subdirs-clean:
- for d in ${SUBDIRS}; do \
- ( cd $$d && ${MAKE} ${MFLAGS} clean ) \
- done
-
-When SUBDIRS is empty, this results in a command like this being passed to
-bash:
-
- for d in ; do
- ( cd $d && ${MAKE} ${MFLAGS} clean )
- done
-
-In versions of bash before bash-2.05a, this was a syntax error. If the
-reserved word `in' was present, a word must follow it before the semicolon
-or newline. The language in the manual page referring to the list of words
-being empty referred to the list after it is expanded. These versions of
-bash required that there be at least one word following the `in' when the
-construct was parsed.
-
-The idiomatic Makefile solution is something like:
-
-SUBDIRS = @SUBDIRS@
-
-subdirs-clean:
- subdirs=$SUBDIRS ; for d in $$subdirs; do \
- ( cd $$d && ${MAKE} ${MFLAGS} clean ) \
- done
-
-The latest drafts of the updated POSIX standard have changed this: the
-word list is no longer required. Bash versions 2.05a and later accept
-the new syntax.
-
-E8) Why does the arithmetic evaluation code complain about `08'?
-
-The bash arithmetic evaluation code (used for `let', $(()), (()), and in
-other places), interprets a leading `0' in numeric constants as denoting
-an octal number, and a leading `0x' as denoting hexadecimal. This is
-in accordance with the POSIX.2 spec, section 2.9.2.1, which states that
-arithmetic constants should be handled as signed long integers as defined
-by the ANSI/ISO C standard.
-
-The POSIX.2 interpretation committee has confirmed this:
-
-http://www.pasc.org/interps/unofficial/db/p1003.2/pasc-1003.2-173.html
-
-E9) Why does the pattern matching expression [A-Z]* match files beginning
- with every letter except `z'?
-
-Bash-2.03, Bash-2.05 and later versions honor the current locale setting
-when processing ranges within pattern matching bracket expressions ([A-Z]).
-This is what POSIX.2 and SUSv3/XPG6 specify.
-
-The behavior of the matcher in bash-2.05 and later versions depends on the
-current LC_COLLATE setting. Setting this variable to `C' or `POSIX' will
-result in the traditional behavior ([A-Z] matches all uppercase ASCII
-characters). Many other locales, including the en_US locale (the default
-on many US versions of Linux) collate the upper and lower case letters like
-this:
-
- AaBb...Zz
-
-which means that [A-Z] matches every letter except `z'. Others collate like
-
- aAbBcC...zZ
-
-which means that [A-Z] matches every letter except `a'.
-
-The portable way to specify upper case letters is [:upper:] instead of
-A-Z; lower case may be specified as [:lower:] instead of a-z.
-
-Look at the manual pages for setlocale(3), strcoll(3), and, if it is
-present, locale(1). If you have locale(1), you can use it to find
-your current locale information even if you do not have any of the
-LC_ variables set.
-
-My advice is to put
-
- export LC_COLLATE=C
-
-into /etc/profile and inspect any shell scripts run from cron for
-constructs like [A-Z]. This will prevent things like
-
- rm [A-Z]*
-
-from removing every file in the current directory except those beginning
-with `z' and still allow individual users to change the collation order.
-Users may put the above command into their own profiles as well, of course.
-
-E10) Why does `cd //' leave $PWD as `//'?
-
-POSIX.2, in its description of `cd', says that *three* or more leading
-slashes may be replaced with a single slash when canonicalizing the
-current working directory.
-
-This is, I presume, for historical compatibility. Certain versions of
-Unix, and early network file systems, used paths of the form
-//hostname/path to access `path' on server `hostname'.
-
-E11) If I resize my xterm while another program is running, why doesn't bash
- notice the change?
-
-This is another issue that deals with job control.
-
-The kernel maintains a notion of a current terminal process group. Members
-of this process group (processes whose process group ID is equal to the
-current terminal process group ID) receive terminal-generated signals like
-SIGWINCH. (For more details, see the JOB CONTROL section of the bash
-man page.)
-
-If a terminal is resized, the kernel sends SIGWINCH to each member of
-the terminal's current process group (the `foreground' process group).
-
-When bash is running with job control enabled, each pipeline (which may be
-a single command) is run in its own process group, different from bash's
-process group. This foreground process group receives the SIGWINCH; bash
-does not. Bash has no way of knowing that the terminal has been resized.
-
-There is a `checkwinsize' option, settable with the `shopt' builtin, that
-will cause bash to check the window size and adjust its idea of the
-terminal's dimensions each time a process stops or exits and returns control
-of the terminal to bash. Enable it with `shopt -s checkwinsize'.
-
-Section F: Things to watch out for on certain Unix versions
-
-F1) Why can't I use command line editing in my `cmdtool'?
-
-The problem is `cmdtool' and bash fighting over the input. When
-scrolling is enabled in a cmdtool window, cmdtool puts the tty in
-`raw mode' to permit command-line editing using the mouse for
-applications that cannot do it themselves. As a result, bash and
-cmdtool each try to read keyboard input immediately, with neither
-getting enough of it to be useful.
-
-This mode also causes cmdtool to not implement many of the
-terminal functions and control sequences appearing in the
-`sun-cmd' termcap entry. For a more complete explanation, see
-that file examples/suncmd.termcap in the bash distribution.
-
-`xterm' is a better choice, and gets along with bash much more
-smoothly.
-
-If you must use cmdtool, you can use the termcap description in
-examples/suncmd.termcap. Set the TERMCAP variable to the terminal
-description contained in that file, i.e.
-
-TERMCAP='Mu|sun-cmd:am:bs:km:pt:li#34:co#80:cl=^L:ce=\E[K:cd=\E[J:rs=\E[s:'
-
-Then export TERMCAP and start a new cmdtool window from that shell.
-The bash command-line editing should behave better in the new
-cmdtool. If this works, you can put the assignment to TERMCAP
-in your bashrc file.
-
-F2) I built bash on Solaris 2. Why do globbing expansions and filename
- completion chop off the first few characters of each filename?
-
-This is the consequence of building bash on SunOS 5 and linking
-with the libraries in /usr/ucblib, but using the definitions
-and structures from files in /usr/include.
-
-The actual conflict is between the dirent structure in
-/usr/include/dirent.h and the struct returned by the version of
-`readdir' in libucb.a (a 4.3-BSD style `struct direct').
-
-Make sure you've got /usr/ccs/bin ahead of /usr/ucb in your $PATH
-when configuring and building bash. This will ensure that you
-use /usr/ccs/bin/cc or acc instead of /usr/ucb/cc and that you
-link with libc before libucb.
-
-If you have installed the Sun C compiler, you may also need to
-put /usr/ccs/bin and /opt/SUNWspro/bin into your $PATH before
-/usr/ucb.
-
-F3) Why does bash dump core after I interrupt username completion or
- `~user' tilde expansion on a machine running NIS?
-
-This is a famous and long-standing bug in the SunOS YP (sorry, NIS)
-client library, which is part of libc.
-
-The YP library code keeps static state -- a pointer into the data
-returned from the server. When YP initializes itself (setpwent),
-it looks at this pointer and calls free on it if it's non-null.
-So far, so good.
-
-If one of the YP functions is interrupted during getpwent (the
-exact function is interpretwithsave()), and returns NULL, the
-pointer is freed without being reset to NULL, and the function
-returns. The next time getpwent is called, it sees that this
-pointer is non-null, calls free, and the bash free() blows up
-because it's being asked to free freed memory.
-
-The traditional Unix mallocs allow memory to be freed multiple
-times; that's probably why this has never been fixed. You can
-run configure with the `--without-gnu-malloc' option to use
-the C library malloc and avoid the problem.
-
-F4) I'm running SVR4.2. Why is the line erased every time I type `@'?
-
-The `@' character is the default `line kill' character in most
-versions of System V, including SVR4.2. You can change this
-character to whatever you want using `stty'. For example, to
-change the line kill character to control-u, type
-
- stty kill ^U
-
-where the `^' and `U' can be two separate characters.
-
-F5) Why does bash report syntax errors when my C News scripts use a
- redirection before a subshell command?
-
-The actual command in question is something like
-
- < file ( command )
-
-According to the grammar given in the POSIX.2 standard, this construct
-is, in fact, a syntax error. Redirections may only precede `simple
-commands'. A subshell construct such as the above is one of the shell's
-`compound commands'. A redirection may only follow a compound command.
-
-This affects the mechanical transformation of commands that use `cat'
-to pipe a file into a command (a favorite Useless-Use-Of-Cat topic on
-comp.unix.shell). While most commands of the form
-
- cat file | command
-
-can be converted to `< file command', shell control structures such as
-loops and subshells require `command < file'.
-
-The file CWRU/sh-redir-hack in the bash-2.05a distribution is an
-(unofficial) patch to parse.y that will modify the grammar to
-support this construct. It will not apply with `patch'; you must
-modify parse.y by hand. Note that if you apply this, you must
-recompile with -DREDIRECTION_HACK. This introduces a large
-number of reduce/reduce conflicts into the shell grammar.
-
-F6) Why can't I use vi-mode editing on Red Hat Linux 6.1?
-
-The short answer is that Red Hat screwed up.
-
-The long answer is that they shipped an /etc/inputrc that only works
-for emacs mode editing, and then screwed all the vi users by setting
-INPUTRC to /etc/inputrc in /etc/profile.
-
-The short fix is to do one of the following: remove or rename
-/etc/inputrc, set INPUTRC=~/.inputrc in ~/.bashrc (or .bash_profile,
-but make sure you export it if you do), remove the assignment to
-INPUTRC from /etc/profile, add
-
- set keymap emacs
-
-to the beginning of /etc/inputrc, or bracket the key bindings in
-/etc/inputrc with these lines
-
- $if mode=emacs
- [...]
- $endif
-
-F7) Why do bash-2.05a and bash-2.05b fail to compile `printf.def' on
- HP/UX 11.x?
-
-HP/UX's support for long double is imperfect at best.
-
-GCC will support it without problems, but the HP C library functions
-like strtold(3) and printf(3) don't actually work with long doubles.
-HP implemented a `long_double' type as a 4-element array of 32-bit
-ints, and that is what the library functions use. The ANSI C
-`long double' type is a 128-bit floating point scalar.
-
-The easiest fix, until HP fixes things up, is to edit the generated
-config.h and #undef the HAVE_LONG_DOUBLE line. After doing that,
-the compilation should complete successfully.
-
-Section G: How can I get bash to do certain common things?
-
-G1) How can I get bash to read and display eight-bit characters?
-
-This is a process requiring several steps.
-
-First, you must ensure that the `physical' data path is a full eight
-bits. For xterms, for example, the `vt100' resources `eightBitInput'
-and `eightBitOutput' should be set to `true'.
-
-Once you have set up an eight-bit path, you must tell the kernel and
-tty driver to leave the eighth bit of characters alone when processing
-keyboard input. Use `stty' to do this:
-
- stty cs8 -istrip -parenb
-
-For old BSD-style systems, you can use
-
- stty pass8
-
-You may also need
-
- stty even odd
-
-Finally, you need to tell readline that you will be inputting and
-displaying eight-bit characters. You use readline variables to do
-this. These variables can be set in your .inputrc or using the bash
-`bind' builtin. Here's an example using `bind':
-
- bash$ bind 'set convert-meta off'
- bash$ bind 'set meta-flag on'
- bash$ bind 'set output-meta on'
-
-The `set' commands between the single quotes may also be placed
-in ~/.inputrc.
-
-G2) How do I write a function `x' to replace builtin command `x', but
- still invoke the command from within the function?
-
-This is why the `command' and `builtin' builtins exist. The
-`command' builtin executes the command supplied as its first
-argument, skipping over any function defined with that name. The
-`builtin' builtin executes the builtin command given as its first
-argument directly.
-
-For example, to write a function to replace `cd' that writes the
-hostname and current directory to an xterm title bar, use
-something like the following:
-
- cd()
- {
- builtin cd "$@" && xtitle "$HOST: $PWD"
- }
-
-This could also be written using `command' instead of `builtin';
-the version above is marginally more efficient.
-
-G3) How can I find the value of a shell variable whose name is the value
- of another shell variable?
-
-Versions of Bash newer than Bash-2.0 support this directly. You can use
-
- ${!var}
-
-For example, the following sequence of commands will echo `z':
-
- var1=var2
- var2=z
- echo ${!var1}
-
-For sh compatibility, use the `eval' builtin. The important
-thing to remember is that `eval' expands the arguments you give
-it again, so you need to quote the parts of the arguments that
-you want `eval' to act on.
-
-For example, this expression prints the value of the last positional
-parameter:
-
- eval echo \"\$\{$#\}\"
-
-The expansion of the quoted portions of this expression will be
-deferred until `eval' runs, while the `$#' will be expanded
-before `eval' is executed. In versions of bash later than bash-2.0,
-
- echo ${!#}
-
-does the same thing.
-
-This is not the same thing as ksh93 `nameref' variables, though the syntax
-is similar. I may add namerefs in a future bash version.
-
-G4) How can I make the bash `time' reserved word print timing output that
- looks like the output from my system's /usr/bin/time?
-
-The bash command timing code looks for a variable `TIMEFORMAT' and
-uses its value as a format string to decide how to display the
-timing statistics.
-
-The value of TIMEFORMAT is a string with `%' escapes expanded in a
-fashion similar in spirit to printf(3). The manual page explains
-the meanings of the escape sequences in the format string.
-
-If TIMEFORMAT is not set, bash acts as if the following assignment had
-been performed:
-
- TIMEFORMAT=$'\nreal\t%3lR\nuser\t%3lU\nsys\t%3lS'
-
-The POSIX.2 default time format (used by `time -p command') is
-
- TIMEFORMAT=$'real %2R\nuser %2U\nsys %2S'
-
-The BSD /usr/bin/time format can be emulated with:
-
- TIMEFORMAT=$'\t%1R real\t%1U user\t%1S sys'
-
-The System V /usr/bin/time format can be emulated with:
-
- TIMEFORMAT=$'\nreal\t%1R\nuser\t%1U\nsys\t%1S'
-
-The ksh format can be emulated with:
-
- TIMEFORMAT=$'\nreal\t%2lR\nuser\t%2lU\nsys\t%2lS'
-
-G5) How do I get the current directory into my prompt?
-
-Bash provides a number of backslash-escape sequences which are expanded
-when the prompt string (PS1 or PS2) is displayed. The full list is in
-the manual page.
-
-The \w expansion gives the full pathname of the current directory, with
-a tilde (`~') substituted for the current value of $HOME. The \W
-expansion gives the basename of the current directory. To put the full
-pathname of the current directory into the path without any tilde
-subsitution, use $PWD. Here are some examples:
-
- PS1='\w$ ' # current directory with tilde
- PS1='\W$ ' # basename of current directory
- PS1='$PWD$ ' # full pathname of current directory
-
-The single quotes are important in the final example to prevent $PWD from
-being expanded when the assignment to PS1 is performed.
-
-G6) How can I rename "*.foo" to "*.bar"?
-
-Use the pattern removal functionality described in D3. The following `for'
-loop will do the trick:
-
- for f in *.foo; do
- mv $f ${f%foo}bar
- done
-
-G7) How can I translate a filename from uppercase to lowercase?
-
-The script examples/functions/lowercase, originally written by John DuBois,
-will do the trick. The converse is left as an exercise.
-
-G8) How can I write a filename expansion (globbing) pattern that will match
- all files in the current directory except "." and ".."?
-
-You must have set the `extglob' shell option using `shopt -s extglob' to use
-this:
-
- echo .!(.|) *
-
-A solution that works without extended globbing is given in the Unix Shell
-FAQ, posted periodically to comp.unix.shell.
-
-Section H: Where do I go from here?
-
-H1) How do I report bugs in bash, and where should I look for fixes and
- advice?
-
-Use the `bashbug' script to report bugs. It is built and
-installed at the same time as bash. It provides a standard
-template for reporting a problem and automatically includes
-information about your configuration and build environment.
-
-`bashbug' sends its reports to bug-bash@gnu.org, which
-is a large mailing list gatewayed to the usenet newsgroup gnu.bash.bug.
-
-Bug fixes, answers to questions, and announcements of new releases
-are all posted to gnu.bash.bug. Discussions concerning bash features
-and problems also take place there.
-
-To reach the bash maintainers directly, send mail to
-bash-maintainers@gnu.org.
-
-H2) What kind of bash documentation is there?
-
-First, look in the doc directory in the bash distribution. It should
-contain at least the following files:
-
-bash.1 an extensive, thorough Unix-style manual page
-builtins.1 a manual page covering just bash builtin commands
-bashref.texi a reference manual in GNU tex`info format
-bashref.info an info version of the reference manual
-FAQ this file
-article.ms text of an article written for The Linux Journal
-readline.3 a man page describing readline
-
-Postscript, HTML, and ASCII files created from the above source are
-available in the documentation distribution.
-
-There is additional documentation available for anonymous FTP from host
-ftp.cwru.edu in the `pub/bash' directory.
-
-Cameron Newham and Bill Rosenblatt have written a book on bash, published
-by O'Reilly and Associates. The book is based on Bill Rosenblatt's Korn
-Shell book. The title is ``Learning the Bash Shell'', and the ISBN number
-is 1-56592-147-X. Look for it in fine bookstores near you. This book
-covers bash-1.14, but has an appendix describing some of the new features
-in bash-2.0.
-
-A second edition of this book is available, published in January, 1998.
-The ISBN number is 1-56592-347-2. Look for it in the same fine bookstores
-or on the web.
-
-The GNU Bash Reference Manual has been published as a printed book by
-Network Theory Ltd (Paperback, ISBN: 0-9541617-7-7, Feb 2003). It covers
-bash-2.0 and is available from most online bookstores (see
-http://www.network-theory.co.uk/bash/manual/ for details). The publisher
-will donate $1 to the Free Software Foundation for each copy sold.
-
-H3) What's coming in future versions?
-
-These are features I hope to include in a future version of bash.
-
-a better bash debugger (a minimally-tested version is included with bash-2.05b)
-associative arrays
-co-processes, but with a new-style syntax that looks like function declaration
-
-H4) What's on the bash `wish list' for future versions?
-
-These are features that may or may not appear in a future version of bash.
-
-breaking some of the shell functionality into embeddable libraries
-a module system like zsh's, using dynamic loading like builtins
-better internationalization using GNU `gettext'
-date-stamped command history
-a bash programmer's guide with a chapter on creating loadable builtins
-a better loadable interface to perl with access to the shell builtins and
- variables (contributions gratefully accepted)
-ksh93-like `nameref' variables
-ksh93-like `+=' variable assignment operator
-ksh93-like `xx.yy' variables (including some of the .sh.* variables) and
- associated disipline functions
-Some of the new ksh93 pattern matching operators, like backreferencing
-
-H5) When will the next release appear?
-
-The next version will appear sometime in 2002. Never make predictions.
-
-
-This document is Copyright 1995-2003 by Chester Ramey.
-
-Permission is hereby granted, without written agreement and
-without license or royalty fees, to use, copy, and distribute
-this document for any purpose, provided that the above copyright
-notice appears in all copies of this document and that the
-contents of this document remain unaltered.
projects / thirdparty / bash.git / commitdiff
