conveniently with @command{xargs}. For example, you can move the files
from the current directory to a sibling directory, @code{d} like this:
-@smallexample
+@example
ls | xargs mv -t ../d --
-@end smallexample
+@end example
However, this doesn't move files whose names begin with @samp{.}.
If you use the GNU @command{find} program, you can move those
Examples:
-@smallexample
+@example
# Output f's contents, then standard input, then g's contents.
cat f - g
# Copy standard input to standard output.
cat
-@end smallexample
+@end example
@node tac invocation
(@samp{-} means standard input), or standard input if none are given.
Synopses:
-@smallexample
+@example
od [@var{option}]@dots{} [@var{file}]@dots{}
od [-abcdfilosx]@dots{} [@var{file}] [[+]@var{offset}[.][b]]
od [@var{option}]@dots{} --traditional [@var{file}]@c
[[+]@var{offset}[.][b] [[+]@var{label}[.][b]]]
-@end smallexample
+@end example
Each line of output consists of the offset in the input, followed by
groups of data from the file. By default, @command{od} prints the offset in
Recognize the non-option label argument that traditional @command{od}
accepted. The following syntax:
-@smallexample
+@example
od --traditional [@var{file}] [[+]@var{offset}[.][b] [[+]@var{label}[.][b]]]
-@end smallexample
+@end example
@noindent
can be used to specify at most one file and optional arguments
printable ASCII characters to represent binary data.
Synopses:
-@smallexample
+@example
base64 [@var{option}]@dots{} [@var{file}]
base64 --decode [@var{option}]@dots{} [@var{file}]
-@end smallexample
+@end example
The base64 encoding expands data to roughly 133% of the original.
The base32 encoding expands data to roughly 160% of the original.
@item
Generate a tags file in case-insensitive sorted order.
-@smallexample
+@example
find src -type f -print0 | sort -z -f | xargs -0 etags --append
-@end smallexample
+@end example
The use of @option{-print0}, @option{-z}, and @option{-0} in this case means
that file names that contain blanks or other special characters are
Choose an output format suitable for @command{nroff} or @command{troff}
processing. Each output line will look like:
-@smallexample
+@example
.xx "@var{tail}" "@var{before}" "@var{keyword_and_after}"@c
"@var{head}" "@var{ref}"
-@end smallexample
+@end example
so it will be possible to write a @samp{.xx} roff macro to take care of
the output typesetting. This is the default output format when GNU
Choose an output format suitable for @TeX{} processing. Each output
line will look like:
-@smallexample
+@example
\xx @{@var{tail}@}@{@var{before}@}@{@var{keyword}@}@c
@{@var{after}@}@{@var{head}@}@{@var{ref}@}
-@end smallexample
+@end example
@noindent
so it will be possible to write a @code{\xx} definition to take care of
wildcard at the start of @var{pattern}. Sometimes it is useful
to give this option several times. For example,
-@smallexample
+@example
$ ls --ignore='.??*' --ignore='.[^.]' --ignore='#*'
-@end smallexample
+@end example
The first option ignores names of length 3 or more that start with @samp{.},
the second ignores all two-character names that start with @samp{.}
will preserve the perceived hard link.
Here is a similar example that exercises @command{cp}'s @option{-L} option:
-@smallexample
+@example
$ mkdir b c; (cd b; : > a; ln -s a b); cp -aL b c; ls -i1 c/b
74163295 a
74163295 b
-@end smallexample
+@end example
@item context
Preserve SELinux security context of the file, or fail with full diagnostics.
Example:
-@smallexample
+@example
ln -srv /a/file /tmp
'/tmp/file' -> '../a/file'
-@end smallexample
+@end example
Relative symbolic links are generated based on their canonicalized
containing directory, and canonicalized targets. I.e., all symbolic
Examples:
-@smallexample
+@example
Bad Example:
# Create link ../a pointing to a in that directory.
# work across networked file systems.
ln -s afile anotherfile
ln -s ../adir/afile yetanotherfile
-@end smallexample
+@end example
@node mkdir invocation
For example, to reflect a user ID numbering change for one user's files
without an option like this, @code{root} might run
-@smallexample
+@example
find / -owner OLDUSER -print0 | xargs -0 chown -h NEWUSER
-@end smallexample
+@end example
But that is dangerous because the interval between when the @command{find}
tests the existing file's owner and when the @command{chown} is actually run
Examples:
-@smallexample
+@example
# Change the owner of /u to "root".
chown root /u
# Change the owner of /u and subfiles to "root".
chown -hR root /u
-@end smallexample
+@end example
@node chgrp invocation
Examples:
-@smallexample
+@example
# Change the group of /u to "staff".
chgrp staff /u
# Change the group of /u and subfiles to "staff".
chgrp -hR staff /u
-@end smallexample
+@end example
@node chmod invocation
is how to convert a piece of text into a shell script which will output
this text in a locale-independent way:
-@smallexample
+@example
$ LC_CTYPE=zh_CN.big5 /usr/local/bin/printf \
'\u4e2d\u6587\n' > sample.txt
$ recode BIG5..JAVA < sample.txt \
| sed -e "s|^|/usr/local/bin/printf '|" -e "s|$|\\\\n'|" \
> sample.sh
-@end smallexample
+@end example
@exitstatus
Examples:
-@smallexample
+@example
# Output "sort".
basename /usr/bin/sort
# Output "stdio" followed by "stdlib"
basename -a -s .h include/stdio.h include/stdlib.h
-@end smallexample
+@end example
@node dirname invocation
Examples:
-@smallexample
+@example
# Output "/usr/bin".
dirname /usr/bin/sort
dirname /usr/bin//.//
# Output ".".
dirname stdio.h
-@end smallexample
+@end example
@node pathchk invocation
To convert such an unwieldy number of seconds back to
a more readable form, use a command like this:
-@smallexample
+@example
# local time zone used
date -d '1970-01-01 UTC 946684800 seconds' +"%Y-%m-%d %T %z"
1999-12-31 19:00:00 -0500
-@end smallexample
+@end example
Or if you do not mind depending on the @samp{@@} feature present since
coreutils 5.3.0, you could shorten this to:
-@smallexample
+@example
date -d @@946684800 +"%F %T %z"
1999-12-31 19:00:00 -0500
-@end smallexample
+@end example
Often it is better to output UTC-relative date and time:
-@smallexample
+@example
date -u -d '1970-01-01 946684800 seconds' +"%Y-%m-%d %T %z"
2000-01-01 00:00:00 +0000
-@end smallexample
+@end example
@item
@cindex leap seconds
parsed reliably. In the following example, @var{release} is
@samp{2.2.18ss.e820-bda652a #4 SMP Tue Jun 5 11:24:08 PDT 2001}:
-@smallexample
+@example
uname -a
@result{} Linux dumdum 2.2.18 #4 SMP Tue Jun 5 11:24:08 PDT 2001 i686@c
unknown unknown GNU/Linux
-@end smallexample
+@end example
The program accepts the following options. Also see @ref{Common options}.
@command{chcon} changes the SELinux security context of the selected files.
Synopses:
-@smallexample
+@example
chcon [@var{option}]@dots{} @var{context} @var{file}@dots{}
chcon [@var{option}]@dots{} [-u @var{user}] [-r @var{role}] [-l @var{range}]@c
[-t @var{type}] @var{file}@dots{}
chcon [@var{option}]@dots{} --reference=@var{rfile} @var{file}@dots{}
-@end smallexample
+@end example
Change the SELinux security context of each @var{file} to @var{context}.
With @option{--reference}, change the security context of each @var{file}
@command{runcon} runs file in specified SELinux security context.
Synopses:
-@smallexample
+@example
runcon @var{context} @var{command} [@var{args}]
runcon [ -c ] [-u @var{user}] [-r @var{role}] [-t @var{type}]@c
[-l @var{range}] @var{command} [@var{args}]
-@end smallexample
+@end example
Run @var{command} with completely-specified @var{context}, or with
current or transitioned security context modified by one or more of @var{level},
With the Unix shell, it's very easy to set up data pipelines:
-@smallexample
+@example
program_to_create_data | filter1 | ... | filterN > final.pretty.data
-@end smallexample
+@end example
We start out by creating the raw data; each filter applies some successive
transformation to the data, until by the time it comes out of the pipeline,
should be treated identically; it's easiest to just get the punctuation out of
the way.
-@smallexample
+@example
$ tr '[:upper:]' '[:lower:]' < whats.gnu | tr -cd '[:alnum:]_ \n' | ...
-@end smallexample
+@end example
The second @command{tr} command operates on the complement of the listed
characters, which are all the letters, the digits, the underscore, and
next step is break the data apart so that we have one word per line. This
makes the counting operation much easier, as we will see shortly.
-@smallexample
+@example
$ tr '[:upper:]' '[:lower:]' < whats.gnu | tr -cd '[:alnum:]_ \n' |
> tr -s ' ' '\n' | ...
-@end smallexample
+@end example
This command turns blanks into newlines. The @option{-s} option squeezes
multiple newline characters in the output into just one, removing
We now have data consisting of one word per line, no punctuation, all one
case. We're ready to count each word:
-@smallexample
+@example
$ tr '[:upper:]' '[:lower:]' < whats.gnu | tr -cd '[:alnum:]_ \n' |
> tr -s ' ' '\n' | sort | uniq -c | ...
-@end smallexample
+@end example
At this point, the data might look something like this:
The final pipeline looks like this:
-@smallexample
+@example
$ tr '[:upper:]' '[:lower:]' < whats.gnu | tr -cd '[:alnum:]_ \n' |
> tr -s ' ' '\n' | sort | uniq -c | sort -n -r
@print{} 156 the
@print{} 51 of
@print{} 51 and
@dots{}
-@end smallexample
+@end example
Whew! That's a lot to digest. Yet, the same principles apply. With six
commands, on two lines (really one long one split for convenience), we've
Now, how to compare our file with the dictionary? As before, we generate
a sorted list of words, one per line:
-@smallexample
+@example
$ tr '[:upper:]' '[:lower:]' < whats.gnu | tr -cd '[:alnum:]_ \n' |
> tr -s ' ' '\n' | sort -u | ...
-@end smallexample
+@end example
Now, all we need is a list of words that are @emph{not} in the
dictionary. Here is where the @command{comm} command comes in.
-@smallexample
+@example
$ tr '[:upper:]' '[:lower:]' < whats.gnu | tr -cd '[:alnum:]_ \n' |
> tr -s ' ' '\n' | sort -u |
> comm -23 - /usr/dict/words
-@end smallexample
+@end example
The @option{-2} and @option{-3} options eliminate lines that are only in the
dictionary (the second file), and lines that are in both files. Lines
projects / thirdparty / coreutils.git / commitdiff
