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NAME
execl, execlp, execle, execv, execvp, execvpe - execute a file
SYNOPSIS
#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
DESCRIPTION
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 a list that includes the directories returned by
confstr(_CS_PATH) (which typically returns the value "/bin:/usr/bin") and possibly also the current
working directory; see NOTES for further details.
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.)
RETURN VALUE
The exec() functions return only if an error has occurred. The return value is -1, and errno is set to
indicate the error.
ERRORS
All of these functions may fail and set errno for any of the errors specified for execve(2).
VERSIONS
The execvpe() function first appeared in glibc 2.11.
ATTRIBUTES
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 │
└───────────────────────────────┴───────────────┴─────────────┘
CONFORMING TO
POSIX.1-2001, POSIX.1-2008.
The execvpe() function is a GNU extension.
NOTES
The default search path (used when the environment does not contain the variable PATH) shows some
variation across systems. It generally includes /bin and /usr/bin (in that order) and may also include
the current working directory. On some other systems, the current working is included after /bin and
/usr/bin, as an anti-Trojan-horse measure. 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 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.
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.
BUGS
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.
SEE ALSO
sh(1), execve(2), execveat(2), fork(2), ptrace(2), fexecve(3), system(3), environ(7)
COLOPHON
This page is part of release 4.15 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 2017-09-15 EXEC(3)