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(guile.info)Processes

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Processes
=========

 - primitive: chdir str
     Change the current working directory to PATH.  The return value is
     unspecified.

 - primitive: getcwd
     Returns the name of the current working directory.

 - primitive: umask [mode]
     If MODE is omitted, retuns a decimal number representing the
     current file creation mask.  Otherwise the file creation mask is
     set to MODE and the previous value is returned.

     E.g., `(umask #o022)' sets the mask to octal 22, decimal 18.

 - primitive: getpid
     Returns an integer representing the current process ID.

 - primitive: getgroups
     Returns a vector of integers representing the current
     supplimentary group IDs.

 - primitive: getppid
     Returns an integer representing the process ID of the parent
     process.

 - primitive: getuid
     Returns an integer representing the current real user ID.

 - primitive: getgid
     Returns an integer representing the current real group ID.

 - primitive: geteuid
     Returns an integer representing the current effective user ID.  If
     the system does not support effective IDs, then the real ID is
     returned.  `(feature? 'EIDs)' reports whether the system supports
     effective IDs.

 - primitive: getegid
     Returns an integer representing the current effective group ID.
     If the system does not support effective IDs, then the real ID is
     returned.  `(feature? 'EIDs)' reports whether the system supports
     effective IDs.

 - primitive: setuid id
     Sets both the real and effective user IDs to the integer ID,
     provided the process has appropriate privileges.  The return value
     is unspecified.

 - primitive: setgid id
     Sets both the real and effective group IDs to the integer ID,
     provided the process has appropriate privileges.  The return value
     is unspecified.

 - primitive: seteuid id
     Sets the effective user ID to the integer ID, provided the process
     has appropriate privileges.  If effective IDs are not supported,
     the real ID is set instead - `(feature? 'EIDs)' reports whether the
     system supports effective IDs.  The return value is unspecified.

 - primitive: setegid id
     Sets the effective group ID to the integer ID, provided the process
     has appropriate privileges.  If effective IDs are not supported,
     the real ID is set instead - `(feature? 'EIDs)' reports whether the
     system supports effective IDs.  The return value is unspecified.

 - primitive: getpgrp
     Returns an integer representing the current process group ID.
     This is the POSIX definition, not BSD.

 - primitive: setpgid pid pgid
     Move the process PID into the process group PGID.  PID or PGID
     must be integers: they can be zero to indicate the ID of the
     current process.  Fails on systems that do not support job control.
     The return value is unspecified.

 - primitive: setsid
     Creates a new session.  The current process becomes the session
     leader and is put in a new process group.  The process will be
     detached from its controlling terminal if it has one.  The return
     value is an integer representing the new process group ID.

 - primitive: waitpid pid [options]
     This procedure collects status information from a child process
     which has terminated or (optionally) stopped.  Normally it will
     suspend the calling process until this can be done.  If more than
     one child process is eligible then one will be chosen by the
     operating system.

     The value of PID determines the behaviour:

    PID greater than 0
          Request status information from the specified child process.

    PID equal to -1 or WAIT_ANY
          Request status information for any child process.

    PID equal to 0 or WAIT_MYPGRP
          Request status information for any child process in the
          current process group.

    PID less than -1
          Request status information for any child process whose
          process group ID is -PID.

     The OPTIONS argument, if supplied, should be the bitwise OR of the
     values of zero or more of the following variables:

      - Variable: WNOHANG
          Return immediately even if there are no child processes to be
          collected.

      - Variable: WUNTRACED
          Report status information for stopped processes as well as
          terminated processes.

     The return value is a pair containing:

       1. The process ID of the child process, or 0 if `WNOHANG' was
          specified and no process was collected.

       2. The integer status value.

The following three functions can be used to decode the process status
code returned by `waitpid'.

 - primitive: status:exit-val status
     Returns the exit status value, as would be set if a process ended
     normally through a call to `exit' or `_exit', if any, otherwise
     `#f'.

 - primitive: status:term-sig status
     Returns the signal number which terminated the process, if any,
     otherwise `#f'.

 - primitive: status:stop-sig status
     Returns the signal number which stopped the process, if any,
     otherwise `#f'.

 - primitive: system [cmd]
     Executes CMD using the operating system's "command processor".
     Under Unix this is usually the default shell `sh'.  The value
     returned is CMD's exit status as returned by `waitpid', which can
     be interpreted using the functions above.

     If `system' is called without arguments, it returns a boolean
     indicating whether the command processor is available.

 - primitive: primitive-exit [status]
     Terminate the current process without unwinding the Scheme stack.
     This is would typically be useful after a fork.  The exit status
     is STATUS if supplied, otherwise zero.

 - primitive: execl filename . args
     Executes the file named by PATH as a new process image.  The
     remaining arguments are supplied to the process; from a C program
     they are accessable as the `argv' argument to `main'.
     Conventionally the first ARG is the same as PATH.  All arguments
     must be strings.

     If ARG is missing, PATH is executed with a null argument list,
     which may have system-dependent side-effects.

     This procedure is currently implemented using the `execv' system
     call, but we call it `execl' because of its Scheme calling
     interface.

 - primitive: execlp filename . args
     Similar to `execl', however if FILENAME does not contain a slash
     then the file to execute will be located by searching the
     directories listed in the `PATH' environment variable.

     This procedure is currently implemented using the `execvp' system
     call, but we call it `execlp' because of its Scheme calling
     interface.

 - primitive: execle filename env . args
     Similar to `execl', but the environment of the new process is
     specified by ENV, which must be a list of strings as returned by
     the `environ' procedure.

     This procedure is currently implemented using the `execve' system
     call, but we call it `execle' because of its Scheme calling
     interface.

 - primitive: primitive-fork
     Creates a new "child" process by duplicating the current "parent"
     process.  In the child the return value is 0.  In the parent the
     return value is the integer process ID of the child.

     This procedure has been renamed from `fork' to avoid a naming
     conflict with the scsh fork.

 - primitive: nice incr
     Increment the priority of the current process by INCR.  A higher
     priority value means that the process runs less often.  The return
     value is unspecified.