execve - execute program


SYNOPSIS

       #include <unistd.h>

       int  execve  (const  char  *filename, char *const argv [],
       char *const envp[]);


DESCRIPTION

       execve() executes the  program  pointed  to  by  filename.
       filename  must  be either a binary executable, or a script
       starting with a line of the form "#!  interpreter  [arg]".
       In  the latter case, the interpreter must be a valid path­
       name for an executable which is not itself a script, which
       will be invoked as interpreter [arg] filename.

       argv  is  an  array  of argument strings passed to the new
       program.  envp is an array of strings,  conventionally  of
       the form key=value, which are passed as environment to the
       new program.  Both, argv and envp must be terminated by  a
       null  pointer.  The argument vector and environment can be
       accessed by the called program's main function, when it is
       defined as int main(int argc, char *argv[], char *envp[]).

       execve() does not return on success, and the  text,  data,
       bss,  and  stack of the calling process are overwritten by
       that of the program loaded.  The program invoked  inherits
       the  calling  process's PID, and any open file descriptors
       that are not set to close on exec.  Signals pending on the
       calling process are cleared.  Any signals set to be caught
       by  the  calling  process  are  reset  to  their   default
       behaviour.

       If the current program is being ptraced, a SIGTRAP is sent
       to it after a successful execve().

       If the set-uid bit is set on the program file  pointed  to
       by  filename  the effective user ID of the calling process
       is changed to that of the owner of the program file.  Sim­
       ilarly,  when  the  set-gid bit of the program file is set
       the effective group ID of the calling process  is  set  to
       the group of the program file.

       If  the  executable  is an a.out dynamically-linked binary
       executable  containing  shared-library  stubs,  the  Linux
       dynamic  linker  ld.so(8) is called at the start of execu­
       tion to bring needed shared libraries into core  and  link
       the executable with them.

       If  the executable is a dynamically-linked ELF executable,
       the interpreter named in the PT_INTERP segment is used  to
       load  the  needed  shared  libraries.  This interpreter is
       linked with the GNU libc version 2.


RETURN VALUE

       On success, execve() does  not  return,  on  error  -1  is
       returned, and errno is set appropriately.


ERRORS

       EACCES The  file  or a script interpreter is not a regular
              file.

       EACCES Execute permission is denied  for  the  file  or  a
              script or ELF interpreter.

       EACCES The file system is mounted noexec.

       EPERM  The  file system is mounted nosuid, the user is not
              the superuser, and the file has an SUID or SGID bit
              set.

       EPERM  The  process  is  being traced, the user is not the
              superuser and the file has an SUID or SGID bit set.

       E2BIG  The argument list is too big.

       ENOEXEC
              An executable is not in a recognised format, is for
              the wrong architecture, or has  some  other  format
              error that means it cannot be executed.

       EFAULT filename  points  outside  your  accessible address
              space.

       ENAMETOOLONG
              filename is too long.

       ENOENT The file filename or a script  or  ELF  interpreter
              does not exist.

       ENOMEM Insufficient kernel memory was available.

       ENOTDIR
              A  component  of  the  path prefix of filename or a
              script or ELF interpreter is not a directory.

       EACCES Search permission is denied on a component  of  the
              path  prefix  of  filename  or the name of a script
              interpreter.

       ELOOP  Too many symbolic links were encountered in resolv­
              ing  filename or the name of a script or ELF inter­
              preter.

              Executable was open for writing by one or more pro­
              cesses.

       EIO    An I/O error occurred.

       ENFILE The  limit on the total number of files open on the
              system has been reached.

       EMFILE The process has the maximum number of files open.

       EINVAL An ELF executable had more than one PT_INTERP  seg­
              ment  (i.e.,  tried  to  name  more than one inter­
              preter).

       EISDIR An ELF interpreter was a directory.

       ELIBBAD
              An ELF interpreter was not in a recognised  format.


CONFORMING TO

       SVr4,  SVID, X/OPEN, BSD 4.3.  POSIX does not document the
       #!  behavior but is otherwise compatible.  SVr4  documents
       additional  error  conditions EAGAIN, EINTR, ELIBACC, ENO­
       LINK, EMULTIHOP; POSIX does not document  ETXTBSY,  EPERM,
       EFAULT,  ELOOP,  EIO,  ENFILE,  EMFILE,  EINVAL, EISDIR or
       ELIBBAD error conditions.


NOTES

       SUID and SGID processes can not be ptrace()d SUID or SGID.

       A maximum line length of 127 characters is allowed for the
       first line in a #! executable shell script.

       Linux ignores the SUID and SGID bits on scripts.


SEE ALSO

       chmod(2), fork(2), execl(3), environ(5), ld.so(8)