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);
Feature Test Macro Requirements for glibc (see feature_test_macros
() family of functions replaces the current process image with a
new process image. The functions described in this manual page are front-ends
(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
The functions can be grouped based on the letters following the "exec"
The const char *arg
and subsequent ellipses can be thought of as
, ..., 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
terminated by a null pointer.
The environment of the caller is specified via the argument envp
argument is an array of pointers to null-terminated strings and
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
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.
If the specified filename includes a slash character, then PATH
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
set to EACCES
If the header of a file isn't recognized (the attempted execve
with the error ENOEXEC
), these functions will execute the shell
) 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.
() 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
() function first appeared in glibc 2.11.
For an explanation of the terms used in this section, see attributes
|execl (), execle (), execv ()
|execlp (), execvp (), execvpe ()
() function is a GNU extension.
The default search path (used when the environment does not contain the variable
) shows some variation across systems. It generally includes
(in that order) and may also include the
current working directory. On some other systems, the current working is
included after /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
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
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
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
employed by the execv
() wrapper function on those