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NAME    [Toc]    [Back]

       execve - execute program

SYNOPSIS    [Toc]    [Back]

       #include <unistd.h>

       int  execve  (const  char  *filename,  char *const argv [], char *const

DESCRIPTION    [Toc]    [Back]

       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 signal
 (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 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 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 typically /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    [Toc]    [Back]

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

ERRORS    [Toc]    [Back]

       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

       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    [Toc]    [Back]
	      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    [Toc]    [Back]
	      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

       ENOMEM Insufficient kernel memory was available.

       ENOTDIR    [Toc]    [Back]
	      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    [Toc]    [Back]
	      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    [Toc]    [Back]
	      An ELF interpreter was not in a recognised format.

CONFORMING TO    [Toc]    [Back]

       SVr4, SVID, X/OPEN, BSD 4.3.  POSIX does not document the #!   behavior
       but  is	otherwise  compatible.	SVr4 documents additional error conditions
       or ELIBBAD error conditions.

NOTES    [Toc]    [Back]

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

       Linux ignores the SUID and SGID bits on scripts.

       The result of mounting a filesystem nosuid vary	between  Linux	kernel
       versions: some will refuse execution of SUID/SGID executables when this
       would give the user powers she did not have already (and return EPERM),
       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    [Toc]    [Back]

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

Linux 2.0.30			  1997-09-03			     EXECVE(2)
[ Back ]
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