execl, execlp, execle, execv, execvp, execvpe - execute a file
extern char **environ;
int execl(const char *pathname, const char *arg, ...
/*, (char *) NULL */);
int execlp(const char *file, const char *arg, ...
/*, (char *) NULL */);
int execle(const char *pathname, const char *arg, ...
/*, (char *) NULL, char *const envp */);
int execv(const char *pathname, char *const argv);
int execvp(const char *file, char *const argv);
int execvpe(const char *file, char *const argv, char *const envp);
The exec() family of functions replaces the current process image with a
new process image. The functions described in this manual page are layered on
top of 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 functions can be grouped based on the letters following the
The const char *arg and subsequent ellipses 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.
By contrast with the 'l' functions, the 'v' functions (below)
specify the command-line arguments of the executed program as a vector.
The 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 must be
terminated by a null pointer.
The environment of the new process image is specified via the argument
envp. The envp argument is an array of pointers to
null-terminated strings and must be terminated by a null pointer.
All other exec() functions (which do not include 'e' in the
suffix) take the environment for the new process image from the external
variable environ in the calling process.
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 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.
execvpe() searches for the program using the value of
PATH from the caller's environment, not from the envp
If the specified filename includes a slash character, then
PATH is ignored, and the file at the specified pathname is
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.)
All other exec() 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.
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).
|execl (), execle (), execv ()
|execlp (), execvp (), execvpe ()
The execvpe() function is a GNU extension.
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
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.
On sparc and sparc64, execv() is provided as a system call by the kernel
(with the prototype shown above) for compatibility with SunOS. This function
is not employed by the execv() wrapper function on those
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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/.