execve (2)

NAME

       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  pathname  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.  The SIGCHLD sig-
       nal (when set to SIG_IGN) may or may not be reset to SIG_DFL.

       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.  Similarly, when the set-gid bit of the pro-
       gram  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 con-
       taining  shared-library  stubs,  the  Linux  dynamic linker ld.so(8) is
       called at the start of execution to bring needed shared libraries  into
       core and link the executable with them.

       If  the  executable  is a dynamically-linked ELF executable, the inter-
       preter named in the PT_INTERP segment is used to load the needed shared
       libraries.   This interpreter is typically /lib/ld-linux.so.1 for bina-
       ries linked with the Linux libc version 5,  or  /lib/ld-linux.so.2  for
       binaries 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.

              ruser, 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  can-
              not 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,
              or a shared library needed for file  or  interpreter  cannot  be
              found.

       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 resolving filename
              or the name of a script or ELF interpreter.

       ETXTBSY
              Executable was open for writing by one or more processes.

       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 segment (i.e.,
              tried to name more than one interpreter).

       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 condi-
       tions EAGAIN, EINTR, ELIBACC, ENOLINK, EMULTIHOP; POSIX does not  docu-
       ment ETXTBSY, EPERM, EFAULT, ELOOP, EIO, ENFILE, EMFILE, EINVAL, EISDIR
       or ELIBBAD error conditions.
       some will just ignore the SUID/SGID bits and exec successfully.

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

SEE ALSO

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

Linux 2.0.30                      1997-09-03                         execve(2)