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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | ATTRIBUTES | CONFORMING TO | NOTES | BUGS | SEE ALSO | COLOPHON |
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, ...
/* (char *) NULL */);
int execlp(const char *file, const char *arg, ...
/* (char *) NULL */);
int execle(const char *path, const char *arg, ...
/*, (char *) NULL, 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.
Special semantics for execlp() and execvp()
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 return only if an error has 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.
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────────┬───────────────┬─────────────┐
│Interface │ Attribute │ Value │
├──────────────────────────────┼───────────────┼─────────────┤
│execl(), execle(), execv() │ Thread safety │ MT-Safe │
├──────────────────────────────┼───────────────┼─────────────┤
│execlp(), execvp(), execvpe() │ Thread safety │ MT-Safe env │
└──────────────────────────────┴───────────────┴─────────────┘
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.
Before glibc 2.24, execl() and execle() employed realloc(3)
internally and were consequently not async-signal-safe, in violation
of the requirements of POSIX.1. This was fixed in glibc 2.24.
sh(1), execve(2), execveat(2), fork(2), ptrace(2), fexecve(3),
system(3), environ(7)
This page is part of release 4.12 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
GNU 2017-03-13 EXEC(3)
Pages that refer to this page: xargs(1), execve(2), getpid(2), ptrace(2), seccomp(2), statfs(2), vfork(2), atexit(3), clearenv(3), confstr(3), glob(3), lttng-ust(3), on_exit(3), pam_getenvlist(3), posix_spawn(3), statvfs(3), stdin(3), sysconf(3), system(3), systemd.exec(5), environ(7), signal-safety(7)