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EXECVE(2)		   Linux Programmer's Manual		     EXECVE(2)

       execve -	execute	program

       #include	<unistd.h>

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

       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 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/ for bina-
       ries linked with	the Linux libc version 5,  or  /lib/  for
       binaries	linked with the	GNU libc version 2.

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

       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 in-

       EACCES The file system is mounted noexec.

       EPERM  The  file	 system	 is  mounted nosuid, the user is not the supe-
	      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.

	      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.

	      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.

	      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.

	      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.

	      An ELF interpreter was not in a recognised format.

       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-
       or ELIBBAD error	conditions.

       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.

       chmod(2), fork(2), execl(3), environ(5),

Linux 2.0.30			  1997-09-03			     EXECVE(2)


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