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[]);

   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  the  current  directory followed by the list of
       directories  returned  by  confstr(_CS_PATH).   (This  confstr(3)  call  typically  returns   the   value
       "/bin:/usr/bin".)

       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.

CONFORMING TO

       POSIX.1-2001, POSIX.1-2008.

       The execvpe() function is a GNU extension.

NOTES

       On  some  other  systems, the default path (used when the environment does not contain the variable PATH)
       has the current working directory listed after /bin and /usr/bin, as an anti-Trojan-horse measure.  Linux
       uses here the traditional "current directory first" default path.

       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.

SEE ALSO

       sh(1), execve(2), fork(2), ptrace(2), fexecve(3), environ(7)

COLOPHON

       This page is part of release 3.54 of the Linux man-pages project.  A  description  of  the  project,  and
       information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.