.\" Copyright (c) 1991 The Regents of the University of California.
.\" All rights reserved.
.\"
+.\" %%%LICENSE_START(BSD_4_CLAUSE_UCB)
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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+.\" %%%LICENSE_END
.\"
.\" @(#)exec.3 6.4 (Berkeley) 4/19/91
.\"
.\" Modified, 24 Jun 2004, Michael Kerrisk <mtk.manpages@gmail.com>
.\" Added note on casting NULL
.\"
-.TH EXEC 3 2010-09-23 "GNU" "Linux Programmer's Manual"
+.TH EXEC 3 2019-08-02 "GNU" "Linux Programmer's Manual"
.SH NAME
-execl, execlp, execle, execv, execvp \- execute a file
+execl, execlp, execle, execv, execvp, execvpe \- execute a file
.SH SYNOPSIS
+.nf
.B #include <unistd.h>
-.sp
+.PP
.B extern char **environ;
-.sp
-.BI "int execl(const char *" path ", const char *" arg ", ...);"
-.br
-.BI "int execlp(const char *" file ", const char *" arg ", ...);"
-.br
-.BI "int execle(const char *" path ", const char *" arg ,
-.br
-.BI " ..., char * const " envp "[]);"
-.br
-.BI "int execv(const char *" path ", char *const " argv "[]);"
-.br
+.PP
+.BI "int execl(const char *" pathname ", const char *" arg ", ..."
+.B " /* (char *) NULL */);"
+.BI "int execlp(const char *" file ", const char *" arg ", ..."
+.B " /* (char *) NULL */);"
+.BI "int execle(const char *" pathname ", const char *" arg ", ..."
+.BI " /*, (char *) NULL, char * const " envp "[] */);"
+.BI "int execv(const char *" pathname ", char *const " argv "[]);"
.BI "int execvp(const char *" file ", char *const " argv "[]);"
+.BI "int execvpe(const char *" file ", char *const " argv "[],"
+.BI " char *const " envp "[]);"
+.fi
+.PP
+.in -4n
+Feature Test Macro Requirements for glibc (see
+.BR feature_test_macros (7)):
+.in
+.PP
+.BR execvpe ():
+_GNU_SOURCE
.SH DESCRIPTION
The
.BR exec ()
.BR execve (2)
for further details about the replacement of the current process image.)
.PP
-The initial argument for these functions is the pathname of a file which is
+The initial argument for these functions is the name of a file that is
to be executed.
.PP
+The functions can be grouped based on the letters following the "exec" prefix.
+.\"
+.SS l - execl(), execlp(), execle()
+.PP
The
-.I "const char *arg"
-and subsequent ellipses in the
-.BR execl (),
-.BR execlp (),
-and
-.BR execle ()
-functions can be thought of as
+.I "const char\ *arg"
+and subsequent ellipses can be thought of as
.IR arg0 ,
.IR arg1 ,
\&...,
with the file being executed.
The list of arguments
.I must
-be terminated by a NULL
-pointer, and, since these are variadic functions, this pointer must be cast
-.IR "(char *) NULL" .
+be terminated by a null pointer,
+and, since these are variadic functions, this pointer must be cast
+.IR "(char\ *) NULL" .
+.PP
+By contrast with the 'l' functions, the 'v' functions (below) specify the
+command-line arguments of the executed program as a vector.
+.\"
+.SS v - execv(), execvp(), execvpe()
.PP
The
-.BR execv ()
-and
-.BR execvp ()
-functions provide an array of pointers to null-terminated strings that
+.I "char\ *const argv[]"
+argument is an array of pointers to null-terminated strings that
represent the argument list available to the new program.
The first argument, by convention, should point to the filename
associated with the file being executed.
The array of pointers
.I must
-be terminated by a NULL pointer.
+be terminated by a null pointer.
+.SS e - execle(), execvpe()
.PP
+The environment of the caller is specified via the argument
+.IR envp .
The
-.BR execle ()
-function also specifies the environment of the executed process by following
-the NULL
-pointer that terminates the list of arguments in the argument list or the
-pointer to the
-.I argv
-array with an additional argument.
-This additional
+.I envp
argument is an array of pointers to null-terminated strings and
.I must
-be terminated by a NULL pointer.
-The other functions take the environment for the new process
+be terminated by a null pointer.
+.PP
+All other
+.BR exec ()
+functions (which do not include 'e' in the suffix)
+take the environment for the new process
image from the external variable
.I environ
-in the current process.
-.SS Special semantics for execlp() and execvp()
+in the calling process.
+.SS p - execlp(), execvp(), execvpe()
.PP
-The
-.BR execlp ()
-and
-.BR execvp ()
-functions duplicate the actions of the shell in
+These functions duplicate the actions of the shell in
searching for an executable file
if the specified filename does not contain a slash (/) character.
The file is sought in the colon-separated list of directory pathnames
.B PATH
environment variable.
If this variable isn't defined, the path list defaults to
-the current directory followed by the list of directories returned by
-.IR confstr(_CS_PATH) .
-(This
-.BR confstr (3)
-call typically returns the value "/bin:/usr/bin".)
-
-In addition, certain
-errors are treated specially.
+a list that includes the directories returned by
+.IR confstr(_CS_PATH)
+(which typically returns the value "/bin:/usr/bin")
+and possibly also the current working directory;
+see NOTES for further details.
+.PP
+If the specified filename includes a slash character, then
+.B PATH
+is ignored, and the file at the specified pathname is executed.
+.PP
+In addition, certain errors are treated specially.
.PP
If permission is denied for a file (the attempted
.BR execve (2)
.RI ( /bin/sh )
with the path of the file as its first argument.
(If this attempt fails, no further searching is done.)
-.SH "RETURN VALUE"
-If any of the
+.PP
+All other
.BR exec ()
-functions returns, an error will have occurred.
+functions (which do not include 'p' in the suffix)
+take as their first argument a (relative or absolute) pathname
+that identifies the program to be executed.
+.SH RETURN VALUE
+The
+.BR exec ()
+functions return only if an error has occurred.
The return value is \-1, and
.I errno
-will be set to indicate the error.
+is set to indicate the error.
.SH ERRORS
All of these functions may fail and set
.I errno
-for any of the errors specified for the library function
+for any of the errors specified for
.BR execve (2).
-.SH "CONFORMING TO"
-POSIX.1-2001.
+.SH VERSIONS
+The
+.BR execvpe ()
+function first appeared in glibc 2.11.
+.SH ATTRIBUTES
+For an explanation of the terms used in this section, see
+.BR attributes (7).
+.TS
+allbox;
+lbw29 lb lb
+l l l.
+Interface Attribute Value
+T{
+.BR execl (),
+.BR execle (),
+.BR execv ()
+T} Thread safety MT-Safe
+T{
+.BR execlp (),
+.BR execvp (),
+.BR execvpe ()
+T} Thread safety MT-Safe env
+.TE
+.SH CONFORMING TO
+POSIX.1-2001, POSIX.1-2008.
+.PP
+The
+.BR execvpe ()
+function is a GNU extension.
.SH NOTES
-On some other systems the default path (used when the environment
-does not contain the variable \fBPATH\fR) has the current working
-directory listed after
+The default search path (used when the environment
+does not contain the variable \fBPATH\fR)
+shows some variation across systems.
+It generally includes
+.I /bin
+and
+.IR /usr/bin
+(in that order) and may also include the current working directory.
+On some other systems, the current working is included after
.I /bin
and
.IR /usr/bin ,
as an anti-Trojan-horse measure.
-Linux uses here the
-traditional "current directory first" default path.
+The glibc implementation long followed the traditional default where
+the current working directory is included at the start of the search path.
+However, some code refactoring during the development of glibc 2.24
+.\" glibc commit 1eb8930608705702d5746e5491bab4e4429fcb83
+caused the current working directory to be dropped altogether
+from the default search path.
+This accidental behavior change is considered mildly beneficial,
+and won't be reverted.
.PP
The behavior of
.BR execlp ()
upon which they returned.
They now return if any error other than the ones
described above occurs.
-.SH "SEE ALSO"
+.SH BUGS
+Before glibc 2.24,
+.BR execl ()
+and
+.BR execle ()
+employed
+.BR realloc (3)
+internally and were consequently not async-signal-safe,
+in violation of the requirements of POSIX.1.
+.\" https://sourceware.org/bugzilla/show_bug.cgi?id=19534
+This was fixed in glibc 2.24.
+.\"
+.SS Architecture-specific details
+On sparc and sparc64,
+.BR execv ()
+is provided as a system call by the kernel
+(with the prototype shown above)
+for compatibility with SunOS.
+This function is
+.I not
+employed by the
+.BR execv ()
+wrapper function on those architectures.
+.SH SEE ALSO
.BR sh (1),
.BR execve (2),
+.BR execveat (2),
.BR fork (2),
.BR ptrace (2),
.BR fexecve (3),
+.BR system (3),
.BR environ (7)
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