EXECV(3) | Library Functions Manual | EXECV(3)

# 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, ...);

int
`execlp`(const char *file, const char *arg, ...);

int
`execle`(const char *path, const char *arg, ..., 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[]);

# DESCRIPTION

This family of functions replace the current process image with a new process image. The functions described in this manual page are front-ends for the execve(2) system call; see that manual page for detailed information about the replacement of the current process.

The initial argument for these functions is the pathname of a file which 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 NUL-terminated strings that represent the argument list available to the executed program. The first argument, by convention, should point to the file name associated with the file being executed. The list of arguments must be terminated by a null pointer.

The `execv`(), `execvp`() and `execvpe`() functions provide an array of pointers to NUL-terminated strings that represent the argument list available to the new program. The first argument, by convention, should point to the file name associated with the file being executed. The array of pointers must be terminated by a null pointer itself.

The `execle`() and `execvpe`() functions also specify the environment of the executed process by following the null pointer that terminates the list of arguments in the parameter list or the pointer to the argv array with an additional parameter. This additional parameter is an array of pointers to NUL-terminated strings and must be terminated by a null pointer itself. The other functions take the environment for the new process image from the external variable environ in the current process.

Some of these functions have special semantics.

The functions `execlp`(), `execvp`() and `execvpe`() will duplicate the actions of the shell in searching for an executable file if the specified file name does not contain a slash (‘/’) character. The search path is the path specified in the environment by `PATH` variable. If this variable isn't specified, `_PATH_DEFPATH` from `<paths.h>` is used instead, consisting of /usr/bin, /bin, /usr/sbin, /sbin, /usr/X11R6/bin, /usr/local/bin, /usr/local/sbin.

In addition, certain errors are treated specially.

If permission is denied for a file (the attempted execve(2) returned `EACCES`), these functions will continue searching the rest of the search path. If no other file is found, however, they will return with the global variable errno set to `EACCES`.

If the header of a file isn't recognized (the attempted execve(2) returned `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.)

# RETURN VALUES

If any of these functions return, an error has occurred. The return value is -1, and the global variable errno will be set to indicate the error.

# FILES

/bin/sh
  default shell program

# ERRORS

`execl`(), `execle`(), `execlp`(), `execvp`(), and `execvpe`() may fail and set errno for any of the errors specified for the library functions execve(2) and malloc(3).

`execv`() may fail and set errno for any of the errors specified for the library function execve(2).

# SEE ALSO

sh(1), execve(2), fork(2), ktrace(2), ptrace(2), environ(7)

# STANDARDS

Historically, the default path for the `execlp`() and `execvp`() functions was ., /bin, /usr/bin. This was changed to improve security and behaviour.

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.

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.

`execl`(), `execv`(), `execle`(), `execlp`() and `execvp`() conform to IEEE Std 1003.1-1988 (“POSIX.1”). `execvpe`() is a GNU extension.

# HISTORY

The functions `execl`() and `execv`() first appeared in Version 2 AT&T UNIX. A predecessor to `execvp`(), `pexec`(), first appeared in the Programmer's Workbench (PWB/UNIX). The functions `execle`(), `execlp`(), `execve`(), and `execvp`() first appeared in Version 7 AT&T UNIX.

May 13, 2023 | Debian