execl, execlp, execle, execv, execvp, execvpe - execute a file
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)
() family of functions replaces the current process image with a
new process image. The functions described in this manual page are front-ends
. (See the manual page for execve(2)
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 const char *arg
and subsequent ellipses in the execl
(), and execle
() functions 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
(), 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
be terminated by a null pointer.
() and execvpe
() functions allow the caller to specify
the environment of the executed program via the argument envp
argument is an array of pointers to null-terminated strings and
be terminated by a null pointer. The other functions take the
environment for the new process image from the external variable
in the calling process.
(), 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
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)
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(2)
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.)
() 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)
() 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 ()
() 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(3)
internally and were consequently not async-signal-safe, in violation of the
requirements of POSIX.1. This was fixed in glibc 2.24.
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