| NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | CONFORMING TO | NOTES | SEE ALSO | COLOPHON | The Linux Programming Interface |
EXEC(3) Linux Programmer's Manual EXEC(3)
execl, execlp, execle, execv, execvp, execvpe - execute a file
#include <unistd.h>
extern char **environ;
int execl(const char *path, const char *arg, ...);
int execlp(const char *file, const char *arg, ...);
int execle(const char *path, const char *arg,
..., char * const envp[]);
int execv(const char *path, char *const argv[]);
int execvp(const char *file, char *const argv[]);
int execvpe(const char *file, char *const argv[],
char *const envp[]);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
execvpe(): _GNU_SOURCE
The exec() family of functions replaces the current process image with a new
process image. The functions described in this manual page are front-ends for
execve(2). (See the manual page for execve(2) for further details about the
replacement of the current process image.)
The initial argument for these functions is the name of a file that is to be
executed.
The const char *arg and subsequent ellipses in the execl(), execlp(), and
execle() functions can be thought of as arg0, arg1, ..., argn. Together they
describe a list of one or more pointers to null-terminated strings that
represent the argument list available to the executed program. The first
argument, by convention, should point to the filename associated with the file
being executed. The list of arguments must be terminated by a NULL pointer,
and, since these are variadic functions, this pointer must be cast (char *)
NULL.
The execv(), execvp(), and execvpe() functions provide 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 must be
terminated by a NULL pointer.
The execle() and execvpe() functions allow the caller to specify the
environment of the executed program via the argument envp. The envp argument
is an array of pointers to null-terminated strings and must be terminated by a
NULL pointer. The other functions take the environment for the new process
image from the external variable environ in the calling process.
The execlp(), execvp(), and execvpe() 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 specified in the 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 confstr(_CS_PATH). (This
confstr(3) call typically returns the value "/bin:/usr/bin".)
If the specified filename includes a slash character, then PATH is ignored,
and the file at the specified pathname is executed.
In addition, certain errors are treated specially.
If permission is denied for a file (the attempted execve(2) failed with the
error EACCES), these functions will continue searching the rest of the search
path. If no other file is found, however, they will return with errno set to
EACCES.
If the header of a file isn't recognized (the attempted execve(2) failed with
the error ENOEXEC), these functions will execute the shell (/bin/sh) with the
path of the file as its first argument. (If this attempt fails, no further
searching is done.)
The exec() functions only return if an error has have occurred. The return
value is -1, and errno is set to indicate the error.
All of these functions may fail and set errno for any of the errors specified
for execve(2).
The execvpe() function first appeared in glibc 2.11.
POSIX.1-2001, POSIX.1-2008.
The execvpe() function is a GNU extension.
On some other systems, the default path (used when the environment does not
contain the variable PATH) has the current working directory listed after /bin
and /usr/bin, as an anti-Trojan-horse measure. Linux uses here the
traditional "current directory first" default path.
The behavior of execlp() and execvp() when errors occur while attempting to
execute the file is historic practice, but has not traditionally been
documented and is not specified by the POSIX standard. BSD (and possibly
other systems) do an automatic sleep and retry if ETXTBSY is encountered.
Linux treats it as a hard error and returns immediately.
Traditionally, the functions execlp() and execvp() ignored all errors except
for the ones described above and ENOMEM and E2BIG, upon which they returned.
They now return if any error other than the ones described above occurs.
sh(1), execve(2), fork(2), ptrace(2), fexecve(3), environ(7)
This page is part of release 3.32 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can be found
at http://www.kernel.org/doc/man-pages/.
GNU 2010-09-25 EXEC(3)
HTML rendering created 2010-12-03 by Michael Kerrisk, author of The Linux Programming Interface