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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
       variable:

              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
       variable 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
       character, 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 Definitions volume of IEEE Std 1003.1-2001, Chapter 8, Environment
       Variables).  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
       associated 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(),
       execlp(), 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
       successful 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.
       Signals 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.
       Similarly,  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
       notifications  shall  be suppressed. It is unspecified whether the exec
       function 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
       volume 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
              execution 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
       argument.

              #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
       filename 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(),
       execle(), and execve() functions return an [ENOEXEC] error for any file
       not recognizable as executable, including  a  shell  script.  When  the
       execlp()  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
       executable 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
       implementations, 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 signals 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
       table  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
       naturally use would be that in the second row.

       The  ISO C  standard  and  this  volume  of IEEE Std 1003.1-2001 do not
       conflict 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-
       provided 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-
              conforming.

       EINVAL This error condition was added to IEEE Std 1003.1-2001 to  allow
              an  implementation  to  detect  executable  files  generated for
              different architectures, and  indicate  this  situation  to  the
              application. Historical implementations of shells, execvp(), and
              execlp() 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
              executable  for  a  different  architecture is encountered. Some
              historical 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
              practice 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
                  internationalized 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
              currently  open  for  writing  by  some  process. This volume of
              IEEE Std 1003.1-2001  neither  requires   nor   prohibits   this
              behavior.

       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
       implementations 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
       setting  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 .