#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

       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 fur-
       ther 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-termi-
       nated strings that represent the argument list available  to  the  exe-
       cuted  program.  The first argument, by convention, should point to the
       filename associated with the file being executed.  The  list  of  argu-
       ments  must be terminated by a NULL pointer, and, since these are vari-
       adic 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 file-
       name does not contain a slash (/) character.  The file is sought in the
       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.)

       The  exec()  functions  only return if an error has have 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.

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

       The execvpe() function is a GNU extension.

       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  attempt-
       ing 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.

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

       This  page  is  part of release 3.35 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://man7.org/linux/man-pages/.

GNU                               2010-09-25                           EXEC(3)
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