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EXEC(P)			   POSIX Programmer's Manual		       EXEC(P)

NAME
       environ, execl, execv, execle, execve, execlp, execvp - execute a file

SYNOPSIS
       #include <unistd.h>

       extern char **environ;
       int execl(const char *path, const char *arg0, ... /*, (char *)0 */);
       int execv(const char *path, char *const argv[]);
       int execle(const char *path, const char *arg0, ... /*,
	      (char *)0, char *const envp[]*/);
       int execve(const char *path, char *const argv[], char *const envp[]);
       int execlp(const char *file, const char *arg0, ... /*, (char *)0 */);
       int execvp(const char *file, char *const argv[]);

DESCRIPTION
       The  exec  family  of functions shall replace the current process image
       with a new process image. The new image shall  be  constructed  from  a
       regular, executable file called the new process image file. There shall
       be no return from a successful exec, because the calling process	 image
       is overlaid by the new process image.

       When  a	C-language  program  is	 executed as a result of this call, it
       shall be entered as a C-language function call as follows:

	      int main (int argc, char *argv[]);

       where argc is the argument count and argv  is  an  array	 of  character
       pointers	 to the arguments themselves. In addition, the following vari‐
       able:

	      extern char **environ;

       is initialized as a pointer to an array of character  pointers  to  the
       environment strings. The argv and environ arrays are each terminated by
       a null pointer. The null pointer terminating  the  argv	array  is  not
       counted in argc.

       Conforming  multi-threaded applications shall not use the environ vari‐
       able to access or modify	 any  environment  variable  while  any	 other
       thread  is  concurrently modifying any environment variable.  A call to
       any function dependent on any environment variable shall be  considered
       a use of the environ variable to access that environment variable.

       The  arguments  specified  by  a program with one of the exec functions
       shall be passed on to the new process image in the corresponding main()
       arguments.

       The  argument path points to a pathname that identifies the new process
       image file.

       The argument file is used to construct a pathname that  identifies  the
       new  process  image file. If the file argument contains a slash charac‐
       ter, the file argument shall be used as the  pathname  for  this	 file.
       Otherwise, the path prefix for this file is obtained by a search of the
       directories passed as the environment variable PATH (see the Base Defi‐
       nitions	volume	of  IEEE Std 1003.1-2001, Chapter 8, Environment Vari‐
       ables).	If this environment variable is not present,  the  results  of
       the search are implementation-defined.

       There  are two distinct ways in which the contents of the process image
       file may cause the execution to fail, distinguished by the  setting  of
       errno  to either [ENOEXEC] or [EINVAL] (see the ERRORS section). In the
       cases where the other members of the exec  family  of  functions	 would
       fail  and  set  errno to [ENOEXEC], the execlp() and execvp() functions
       shall execute a command interpreter and the environment of the executed
       command shall be as if the process invoked the sh utility using execl()
       as follows:

	      execl(<shell path>, arg0, file, arg1, ..., (char *)0);

       where <shell path> is an unspecified pathname for the sh utility,  file
       is  the	process image file, and for execvp(), where arg0, arg1, and so
       on correspond to the values passed to execvp() in argv[0], argv[1], and
       so on.

       The  arguments  represented by arg0,... are pointers to null-terminated
       character strings. These strings shall  constitute  the	argument  list
       available  to  the  new process image. The list is terminated by a null
       pointer. The argument arg0 should point to a filename that  is  associ‐
       ated with the process being started by one of the exec functions.

       The  argument argv is an array of character pointers to null-terminated
       strings. The application shall ensure that  the	last  member  of  this
       array  is  a  null pointer. These strings shall constitute the argument
       list available to the new process image.	 The value in  argv[0]	should
       point  to  a filename that is associated with the process being started
       by one of the exec functions.

       The argument envp is an array of character pointers to  null-terminated
       strings.	 These	strings	 shall	constitute the environment for the new
       process image. The envp array is terminated by a null pointer.

       For those forms not containing an envp pointer ( execl(), execv(), exe‐
       clp(),  and  execvp()), the environment for the new process image shall
       be taken from the external variable environ in the calling process.

       The number of bytes available for the new  process'  combined  argument
       and  environment	 lists	is  {ARG_MAX}.	It  is	implementation-defined
       whether null terminators, pointers,  and/or  any	 alignment  bytes  are
       included in this total.

       File descriptors open in the calling process image shall remain open in
       the new process image, except  for  those  whose	 close-on-  exec  flag
       FD_CLOEXEC  is  set.  For  those file descriptors that remain open, all
       attributes of the open file description remain unchanged. For any  file
       descriptor  that is closed for this reason, file locks are removed as a
       result of the close as described	 in  close()  .	 Locks	that  are  not
       removed by closing of file descriptors remain unchanged.

       If  file descriptors 0, 1, and 2 would otherwise be closed after a suc‐
       cessful call to one of the  exec	 family	 of  functions,	 and  the  new
       process	image  file has the set-user-ID or set-group-ID file mode bits
       set,    and the ST_NOSUID bit is not set for the file system containing
       the  new	 process  image file,  implementations may open an unspecified
       file for each of these file descriptors in the new process image.

       Directory streams open in the calling process image shall be closed  in
       the new process image.

       The  state  of  the floating-point environment in the new process image
       shall be set to the default.

       The state of conversion descriptors and message catalog descriptors  in
       the  new	 process  image is undefined.	For the new process image, the
       equivalent of:

	      setlocale(LC_ALL, "C")

       shall be executed at start-up.

       Signals set to the default action  (SIG_DFL)  in	 the  calling  process
       image  shall  be	 set  to  the default action in the new process image.
       Except for SIGCHLD, signals set to be ignored (SIG_IGN) by the  calling
       process image shall be set to be ignored by the new process image. Sig‐
       nals set to be caught by the calling process image shall be set to  the
       default	action	in  the	 new  process  image  (see <signal.h>). If the
       SIGCHLD signal is set to be ignored by the calling process image, it is
       unspecified  whether  the SIGCHLD signal is set to be ignored or to the
       default action in the new process image.	  After a successful  call  to
       any  of	the  exec functions, alternate signal stacks are not preserved
       and the SA_ONSTACK flag shall be cleared for all signals.

       After a successful call to any of the  exec  functions,	any  functions
       previously registered by atexit() are no longer registered.

       If  the	ST_NOSUID  bit	is  set for the file system containing the new
       process image file, then the effective user  ID,	 effective  group  ID,
       saved  set-user-ID,  and	 saved	set-group-ID  are unchanged in the new
       process image. Otherwise,  if the  set-user-ID  mode  bit  of  the  new
       process	image  file  is	 set, the effective user ID of the new process
       image shall be set to the user ID of the new process image file.	 Simi‐
       larly,  if  the	set-group-ID mode bit of the new process image file is
       set, the effective group ID of the new process image shall  be  set  to
       the  group  ID  of  the	new process image file. The real user ID, real
       group ID, and supplementary group IDs of the new	 process  image	 shall
       remain  the  same  as those of the calling process image. The effective
       user ID and effective group ID of the new process image shall be	 saved
       (as  the	 saved	set-user-ID  and  the  saved  set-group-ID) for use by
       setuid().

       Any shared memory segments attached to the calling process image	 shall
       not be attached to the new process image.

       Any  named semaphores open in the calling process shall be closed as if
       by appropriate calls to sem_close().

       Any blocks of typed memory that were mapped in the calling process  are
       unmapped, as if munmap() was implicitly called to unmap them.

       Memory locks established by the calling process via calls to mlockall()
       or mlock() shall be removed. If locked pages in the  address  space  of
       the  calling  process  are also mapped into the address spaces of other
       processes and are locked by those processes, the locks  established  by
       the  other processes shall be unaffected by the call by this process to
       the exec function. If the exec function fails,  the  effect  on	memory
       locks is unspecified.

       Memory  mappings created in the process are unmapped before the address
       space is rebuilt for the new process image.

       For the SCHED_FIFO and SCHED_RR scheduling  policies,  the  policy  and
       priority	 settings  shall not be changed by a call to an exec function.
       For other scheduling policies, the policy and priority settings on exec
       are implementation-defined.

       Per-process  timers  created  by	 the  calling process shall be deleted
       before replacing the current process image with the new process image.

       All open message queue descriptors in  the  calling  process  shall  be
       closed, as described in mq_close() .

       Any  outstanding	 asynchronous  I/O  operations	may be canceled. Those
       asynchronous I/O operations that are not canceled shall complete as  if
       the exec function had not yet occurred, but any associated signal noti‐
       fications shall be suppressed. It is unspecified whether the exec func‐
       tion itself blocks awaiting such I/O completion.	 In no event, however,
       shall the new process image created by the exec function be affected by
       the presence of outstanding asynchronous I/O operations at the time the
       exec function is called. Whether any I/O is canceled, and which I/O may
       be canceled upon exec, is implementation-defined.

       The  new	 process image shall inherit the CPU-time clock of the calling
       process image. This inheritance means that the process  CPU-time	 clock
       of the process being exec-ed shall not be reinitialized or altered as a
       result of the exec function other than to reflect the time spent by the
       process executing the exec function itself.

       The  initial  value  of the CPU-time clock of the initial thread of the
       new process image shall be set to zero.

       If the calling process is being traced, the  new	 process  image	 shall
       continue	 to  be	 traced	 into  the  same  trace stream as the original
       process image, but the new process image shall not inherit the  mapping
       of  trace  event names to trace event type identifiers that was defined
       by    calls    to     the     posix_trace_eventid_open()	    or	   the
       posix_trace_trid_eventid_open() functions in the calling process image.

       If the calling process is a trace controller process, any trace streams
       that were created  by  the  calling  process  shall  be	shut  down  as
       described in the posix_trace_shutdown() function.

       The  new	 process  shall inherit at least the following attributes from
       the calling process image:

	* Nice value (see nice() )

	* semadj values (see semop() )

	* Process ID

	* Parent process ID

	* Process group ID

	* Session membership

	* Real user ID

	* Real group ID

	* Supplementary group IDs

	* Time left until an alarm clock signal (see alarm() )

	* Current working directory

	* Root directory

	* File mode creation mask (see umask() )

	* File size limit (see ulimit() )

	* Process signal mask (see sigprocmask() )

	* Pending signal (see sigpending() )

	* tms_utime, tms_stime, tms_cutime, and tms_cstime (see times() )

	* Resource limits

	* Controlling terminal

	* Interval timers

       All   other   process   attributes   defined   in   this	  volume    of
       IEEE Std 1003.1-2001  shall  be	the  same  in  the new and old process
       images. The inheritance of process attributes not defined by this  vol‐
       ume of IEEE Std 1003.1-2001 is implementation-defined.

       A  call	to  any exec function from a process with more than one thread
       shall result in all threads being terminated  and  the  new  executable
       image  being  loaded  and  executed.  No	 destructor functions shall be
       called.

       Upon successful completion, the exec functions shall  mark  for	update
       the st_atime field of the file. If an exec function failed but was able
       to locate the process image file, whether the st_atime field is	marked
       for  update  is	unspecified.  Should  the  exec	 function succeed, the
       process image file shall be considered to have been opened with open().
       The  corresponding close() shall be considered to occur at a time after
       this open, but before process termination or successful completion of a
       subsequent  call	 to  one  of  the  exec	 functions,  posix_spawn(), or
       posix_spawnp().	The argv[] and	envp[]	arrays	of  pointers  and  the
       strings	to which those arrays point shall not be modified by a call to
       one of the exec functions, except as a  consequence  of	replacing  the
       process image.

       The saved resource limits in the new process image are set to be a copy
       of the process' corresponding hard and soft limits.

RETURN VALUE
       If one of the exec functions returns to the calling process  image,  an
       error  has  occurred;  the return value shall be -1, and errno shall be
       set to indicate the error.

ERRORS
       The exec functions shall fail if:

       E2BIG  The number of bytes used by the  new  process  image's  argument
	      list  and	 environment  list  is greater than the system-imposed
	      limit of {ARG_MAX} bytes.

       EACCES Search permission is denied for a directory listed  in  the  new
	      process  image file's path prefix, or the new process image file
	      denies execution permission, or the new process  image  file  is
	      not  a regular file and the implementation does not support exe‐
	      cution of files of its type.

       EINVAL The new process image file has the  appropriate  permission  and
	      has  a  recognized executable binary format, but the system does
	      not support execution of a file with this format.

       ELOOP  A loop exists in symbolic links encountered during resolution of
	      the path or file argument.

       ENAMETOOLONG
	      The length of the path or file arguments exceeds {PATH_MAX} or a
	      pathname component is longer than {NAME_MAX}.

       ENOENT A component of path or file does not name an  existing  file  or
	      path or file is an empty string.

       ENOTDIR
	      A component of the new process image file's path prefix is not a
	      directory.

       The exec functions, except for execlp() and execvp(), shall fail if:

       ENOEXEC
	      The new process image file has the appropriate access permission
	      but has an unrecognized format.

       The exec functions may fail if:

       ELOOP  More  than  {SYMLOOP_MAX} symbolic links were encountered during
	      resolution of the path or file argument.

       ENAMETOOLONG
	      As a result of encountering a symbolic link in resolution of the
	      path  argument,  the  length  of the substituted pathname string
	      exceeded {PATH_MAX}.

       ENOMEM The new process image requires more memory than  is  allowed  by
	      the hardware or system-imposed memory management constraints.

       ETXTBSY
	      The  new	process	 image	file is a pure procedure (shared text)
	      file that is currently open for writing by some process.

       The following sections are informative.

EXAMPLES
   Using execl()
       The following example executes the ls command, specifying the  pathname
       of  the	executable ( /bin/ls) and using arguments supplied directly to
       the command to produce single-column output.

	      #include <unistd.h>

	      int ret;
	      ...
	      ret = execl ("/bin/ls", "ls", "-1", (char *)0);

   Using execle()
       The following example is similar to Using execl()  .  In	 addition,  it
       specifies the environment for the new process image using the env argu‐
       ment.

	      #include <unistd.h>

	      int ret;
	      char *env[] = { "HOME=/usr/home", "LOGNAME=home", (char *)0 };
	      ...
	      ret = execle ("/bin/ls", "ls", "-l", (char *)0, env);

   Using execlp()
       The following example searches for the location of the ls command among
       the directories specified by the PATH environment variable.

	      #include <unistd.h>

	      int ret;
	      ...
	      ret = execlp ("ls", "ls", "-l", (char *)0);

   Using execv()
       The  following  example	passes	arguments to the ls command in the cmd
       array.

	      #include <unistd.h>

	      int ret;
	      char *cmd[] = { "ls", "-l", (char *)0 };
	      ...
	      ret = execv ("/bin/ls", cmd);

   Using execve()
       The following example passes arguments to the ls	 command  in  the  cmd
       array,  and  specifies  the environment for the new process image using
       the env argument.

	      #include <unistd.h>

	      int ret;
	      char *cmd[] = { "ls", "-l", (char *)0 };
	      char *env[] = { "HOME=/usr/home", "LOGNAME=home", (char *)0 };
	      ...
	      ret = execve ("/bin/ls", cmd, env);

   Using execvp()
       The following example searches for the location of the ls command among
       the  directories specified by the PATH environment variable, and passes
       arguments to the ls command in the cmd array.

	      #include <unistd.h>

	      int ret;
	      char *cmd[] = { "ls", "-l", (char *)0 };
	      ...
	      ret = execvp ("ls", cmd);

APPLICATION USAGE
       As the state of conversion descriptors and message catalog  descriptors
       in  the	new process image is undefined, conforming applications should
       not rely on their use and should close them prior to calling one of the
       exec functions.

       Applications  that  require  other than the default POSIX locale should
       call setlocale() with  the  appropriate	parameters  to	establish  the
       locale of the new process.

       The environ array should not be accessed directly by the application.

       Applications  should  not  depend on file descriptors 0, 1, and 2 being
       closed after an exec. A future version may allow these file descriptors
       to be automatically opened for any process.

RATIONALE
       Early  proposals	 required  that	 the value of argc passed to main() be
       "one or greater". This was driven by the same requirement in drafts  of
       the  ISO C  standard. In fact, historical implementations have passed a
       value of zero when no arguments are supplied to the caller of the  exec
       functions.   This  requirement  was removed from the ISO C standard and
       subsequently removed from this volume of IEEE Std 1003.1-2001 as	 well.
       The  wording,  in  particular  the  use	of the word should, requires a
       Strictly Conforming POSIX Application to pass at least one argument  to
       the  exec  function, thus guaranteeing that argc be one or greater when
       invoked by such an application. In fact, this is good  practice,	 since
       many existing applications reference argv[0] without first checking the
       value of argc.

       The requirement on a Strictly Conforming POSIX Application also	states
       that  the  value	 passed as the first argument be a filename associated
       with the process being started.	Although  some	existing  applications
       pass  a	pathname rather than a filename in some circumstances, a file‐
       name is more generally useful, since the common usage of argv[0] is  in
       printing	 diagnostics.  In  some	 cases	the filename passed is not the
       actual filename of the file; for example, many implementations  of  the
       login  utility  use  a  convention of prefixing a hyphen ( '-' ) to the
       actual filename, which  indicates  to  the  command  interpreter	 being
       invoked that it is a "login shell".

       Historically  there  have  been	two ways that implementations can exec
       shell scripts.

       One common historical implementation is that the execl(), execv(), exe‐
       cle(),  and  execve()  functions return an [ENOEXEC] error for any file
       not recognizable as executable, including a shell script. When the exe‐
       clp()  and  execvp()  functions	encounter such a file, they assume the
       file to be a shell script and invoke a  known  command  interpreter  to
       interpret  such	files.	This  is now required by IEEE Std 1003.1-2001.
       These implementations of execvp() and execlp() only give the  [ENOEXEC]
       error in the rare case of a problem with the command interpreter's exe‐
       cutable file. Because of these implementations, the [ENOEXEC] error  is
       not  mentioned  for  execlp() or execvp(), although implementations can
       still give it.

       Another way that some historical implementations handle	shell  scripts
       is  by  recognizing  the	 first	two bytes of the file as the character
       string "#!" and using the remainder of the first line of	 the  file  as
       the name of the command interpreter to execute.

       One  potential  source of confusion noted by the standard developers is
       over how the contents of a process image file affect  the  behavior  of
       the  exec  family  of  functions. The following is a description of the
       actions taken:

	1. If the process image file is a valid executable (in a  format  that
	   is executable and valid and having appropriate permission) for this
	   system, then the system executes the file.

	2. If the process image file has appropriate permission and  is	 in  a
	   format  that is executable but not valid for this system (such as a
	   recognized binary for another architecture), then this is an	 error
	   and errno is set to [EINVAL] (see later RATIONALE on [EINVAL]).

	3. If  the  process  image  file has appropriate permission but is not
	   otherwise recognized:

	    a. If this is a call to execlp() or execvp(), then they  invoke  a
	       command	interpreter  assuming that the process image file is a
	       shell script.

	    b. If this is not a call to execlp() or execvp(),  then  an	 error
	       occurs and errno is set to [ENOEXEC].

       Applications  that do not require to access their arguments may use the
       form:

	      main(void)
       as specified in the ISO C standard. However,  the  implementation  will
       always  provide	the  two arguments argc and argv, even if they are not
       used.

       Some implementations provide a third argument to	 main()	 called	 envp.
       This  is	 defined  as  a pointer to the environment. The ISO C standard
       specifies invoking main() with two arguments, so	 implementations  must
       support	 applications	written	  this	 way.  Since  this  volume  of
       IEEE Std 1003.1-2001 defines the global variable environ, which is also
       provided	 by  historical	 implementations and can be used anywhere that
       envp could be used, there is no functional need for the envp  argument.
       Applications should use the getenv() function rather than accessing the
       environment directly via either envp or	environ.  Implementations  are
       required	 to  support  the two-argument calling sequence, but this does
       not prohibit an implementation from  supporting	envp  as  an  optional
       third argument.

       This  volume  of	 IEEE Std 1003.1-2001  specifies  that	signals set to
       SIG_IGN remain set to SIG_IGN, and that	the  process  signal  mask  be
       unchanged  across an exec. This is consistent with historical implemen‐
       tations, and it permits some useful functionality, such	as  the	 nohup
       command.	 However,  it  should be noted that many existing applications
       wrongly assume that they start with certain signals set to the  default
       action  and/or  unblocked.  In  particular, applications written with a
       simpler signal model that does not include blocking of signals, such as
       the  one in the ISO C standard, may not behave properly if invoked with
       some signals blocked. Therefore, it is best not to block or ignore sig‐
       nals  across execs without explicit reason to do so, and especially not
       to block signals across execs of arbitrary (not	closely	 co-operating)
       programs.

       The  exec  functions always save the value of the effective user ID and
       effective group ID of the  process  at  the  completion	of  the	 exec,
       whether	or  not the set-user-ID or the set-group-ID bit of the process
       image file is set.

       The statement about argv[] and envp[] being constants  is  included  to
       make explicit to future writers of language bindings that these objects
       are completely constant. Due to a limitation of the ISO C standard,  it
       is not possible to state that idea in standard C. Specifying two levels
       of const- qualification for the argv[] and envp[]  parameters  for  the
       exec  functions	may  seem  to  be the natural choice, given that these
       functions do not modify either the array of pointers or the  characters
       to  which the function points, but this would disallow existing correct
       code. Instead, only the array of pointers is noted as constant. The ta‐
       ble  of	assignment  compatibility  for dst= src derived from the ISO C
       standard summarizes the compatibility:

    dst:		char *[] const char *[] char *const[] const char *const[]
    src:
    char *[]		VALID	 -		VALID	      -
    const char *[]	-	 VALID		-	      VALID
    char * const []	-	 -		VALID	      -
    const char *const[] -	 -		-	      VALID

       Since all existing code has a source type matching the first  row,  the
       column  that gives the most valid combinations is the third column. The
       only other possibility is the fourth column, but using it would require
       a cast on the argv or envp arguments. It is unfortunate that the fourth
       column cannot be used, because the declaration a non-expert would natu‐
       rally use would be that in the second row.

       The  ISO C standard and this volume of IEEE Std 1003.1-2001 do not con‐
       flict on the use of environ, but	 some  historical  implementations  of
       environ	may  cause  a  conflict.  As long as environ is treated in the
       same way as an entry point (for example, fork()), it conforms  to  both
       standards.   A  library can contain fork(), but if there is a user-pro‐
       vided fork(), that fork() is given precedence and  no  problem  ensues.
       The  situation is similar for environ: the definition in this volume of
       IEEE Std 1003.1-2001 is to be used if there is no user-provided environ
       to  take precedence.  At least three implementations are known to exist
       that solve this problem.

       E2BIG  The limit {ARG_MAX} applies not just to the size of the argument
	      list,  but  to  the  sum of that and the size of the environment
	      list.

       EFAULT Some historical systems return [EFAULT]  rather  than  [ENOEXEC]
	      when  the new process image file is corrupted. They are non-con‐
	      forming.

       EINVAL This error condition was added to IEEE Std 1003.1-2001 to	 allow
	      an  implementation to detect executable files generated for dif‐
	      ferent architectures, and indicate this situation to the	appli‐
	      cation. Historical implementations of shells, execvp(), and exe‐
	      clp() that encounter an [ENOEXEC] error will execute a shell  on
	      the  assumption  that  the file is a shell script. This will not
	      produce the desired effect when the file is a  valid  executable
	      for  a  different architecture. An implementation may now choose
	      to avoid this problem by returning [EINVAL] when	a  valid  exe‐
	      cutable  for  a different architecture is encountered. Some his‐
	      torical implementations return [EINVAL]  to  indicate  that  the
	      path  argument contains a character with the high order bit set.
	      The standard developers chose to deviate from  historical	 prac‐
	      tice for the following reasons:

	       1. The new utilization of [EINVAL] will provide some measure of
		  utility to the user community.

	       2. Historical use of [EINVAL] is not acceptable in an  interna‐
		  tionalized operating environment.

       ENAMETOOLONG
	      Since the file pathname may be constructed by taking elements in
	      the PATH variable and putting them together with	the  filename,
	      the  [ENAMETOOLONG]  error  condition could also be reached this
	      way.

       ETXTBSY
	      System V returns this error when the  executable	file  is  cur‐
	      rently  open  for	 writing  by  some  process.  This  volume  of
	      IEEE Std 1003.1-2001 neither requires nor prohibits this	behav‐
	      ior.

       Other systems (such as System V) may return [EINTR] from exec.  This is
       not addressed by this volume of IEEE Std 1003.1-2001,  but  implementa‐
       tions  may  have	 a window between the call to exec and the time that a
       signal could cause one of the exec calls to return with [EINTR].

       An explicit statement  regarding	 the  floating-point  environment  (as
       defined	in  the	 <fenv.h>  header) was added to make it clear that the
       floating-point environment is set to its default when a call to one  of
       the  exec functions succeeds.  The requirements for inheritance or set‐
       ting to the default for other process and thread start-up functions  is
       covered	by  more  generic  statements in their descriptions and can be
       summarized as follows:

       posix_spawn()
	      Set to default.

       fork() Inherit.

       pthread_create()
	      Inherit.

FUTURE DIRECTIONS
       None.

SEE ALSO
       alarm() , atexit() , chmod() , close() , exit() , fcntl()  ,  fork()  ,
       fstatvfs()  ,  getenv() , getitimer() , getrlimit() , mmap() , nice() ,
       posix_spawn() , posix_trace_eventid_open() ,  posix_trace_shutdown()  ,
       posix_trace_trid_eventid_open()	,  putenv()  , semop() , setlocale() ,
       shmat() , sigaction() , sigaltstack() , sigpending() , sigprocmask()  ,
       system()	 ,  times() , ulimit() , umask() , the Base Definitions volume
       of  IEEE Std 1003.1-2001,  Chapter  11,	General	 Terminal   Interface,
       <unistd.h>

COPYRIGHT
       Portions	 of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       --  Portable  Operating	System	Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003	by  the	 Institute  of
       Electrical  and	Electronics  Engineers, Inc and The Open Group. In the
       event of any discrepancy between this version and the original IEEE and
       The  Open Group Standard, the original IEEE and The Open Group Standard
       is the referee document. The original Standard can be  obtained	online
       at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group		     2003			       EXEC(P)
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