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.

     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
     parent 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 executable is an a.out dynamically-linked binary exe-
     cutable  containing  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  interpreter  named  in the PT_INTERP segment is used to
     load the needed shared libraries.  This interpreter is typi-
     cally  /lib/ld-linux.so.1 for binaries 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.

ERRORS

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

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

     ETXTBUSY
             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  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 addi-
     tional error conditions  EAGAIN,  EINTR,  ELIBACC,  ENOLINK,
     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

     ld.so(8), execl(3), fork(2)