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NOHUP(1P)                  POSIX Programmer's Manual                 NOHUP(1P)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may dif-
       fer (consult the corresponding Linux manual page for details of Linux behavior), or the interface  may  not  be
       implemented on Linux.

NAME
       nohup - invoke a utility immune to hangups

SYNOPSIS
       nohup utility [argument...]

DESCRIPTION
       The nohup utility shall invoke the utility named by the utility operand with arguments supplied as the argument
       operands. At the time the named utility is invoked, the SIGHUP signal shall be set to be ignored.

       If the standard output is a terminal, all output written by the named utility to its standard output  shall  be
       appended  to  the  end of the file nohup.out in the current directory. If nohup.out cannot be created or opened
       for appending, the output shall be appended to the end of the file nohup.out in the directory specified by  the
       HOME  environment  variable.  If  neither  file  can  be  created or opened for appending, utility shall not be
       invoked. If a file is created, the file's permission bits shall be set to S_IRUSR | S_IWUSR.

       If the standard error is a terminal, all output written by the named utility to its  standard  error  shall  be
       redirected to the same file descriptor as the standard output.

OPTIONS
       None.

OPERANDS
       The following operands shall be supported:

       utility
              The  name  of  a utility that is to be invoked. If the utility operand names any of the special built-in
              utilities in Special Built-In Utilities, the results are undefined.

       argument
              Any string to be supplied as an argument when invoking the utility named by the utility operand.


STDIN
       Not used.

INPUT FILES
       None.

ENVIRONMENT VARIABLES
       The following environment variables shall affect the execution of nohup:

       HOME   Determine the pathname of the user's home directory: if the output file nohup.out cannot be  created  in
              the current directory, the nohup utility shall use the directory named by HOME to create the file.

       LANG   Provide  a  default  value  for the internationalization variables that are unset or null. (See the Base
              Definitions volume of IEEE Std 1003.1-2001, Section 8.2, Internationalization Variables for  the  prece-
              dence of internationalization variables used to determine the values of locale categories.)

       LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables.

       LC_CTYPE
              Determine the locale for the interpretation of sequences of bytes of text data as characters (for  exam-
              ple, single-byte as opposed to multi-byte characters in arguments).

       LC_MESSAGES
              Determine  the locale that should be used to affect the format and contents of diagnostic messages writ-
              ten to standard error.

       NLSPATH
              Determine the location of message catalogs for the processing of LC_MESSAGES .

       PATH   Determine the search path that is used to locate the utility to be invoked.  See  the  Base  Definitions
              volume of IEEE Std 1003.1-2001, Chapter 8, Environment Variables.


ASYNCHRONOUS EVENTS
       The nohup utility shall take the standard action for all signals except that SIGHUP shall be ignored.

STDOUT
       If  the  standard output is not a terminal, the standard output of nohup shall be the standard output generated
       by the execution of the utility specified by the operands. Otherwise, nothing shall be written to the  standard
       output.

STDERR
       If  the standard output is a terminal, a message shall be written to the standard error, indicating the name of
       the file to which the  output  is  being  appended.  The  name  of  the  file  shall  be  either  nohup.out  or
       $HOME/nohup.out.

OUTPUT FILES
       If  the standard output is a terminal, all output written by the named utility to the standard output and stan-
       dard error is appended to the file nohup.out, which is created if it does not already exist.

EXTENDED DESCRIPTION
       None.

EXIT STATUS
       The following exit values shall be returned:

       126    The utility specified by utility was found but could not be invoked.

       127    An error occurred in the nohup utility or the utility specified by utility could not be found.


       Otherwise, the exit status of nohup shall be that of the utility specified by the utility operand.

CONSEQUENCES OF ERRORS
       Default.

       The following sections are informative.

APPLICATION USAGE
       The command, env, nice, nohup, time, and xargs utilities have been specified to use exit code 127 if  an  error
       occurs  so  that  applications can distinguish "failure to find a utility" from "invoked utility exited with an
       error indication". The value 127 was chosen because it is not commonly used for other meanings; most  utilities
       use small values for "normal error conditions" and the values above 128 can be confused with termination due to
       receipt of a signal. The value 126 was chosen in a similar manner to indicate that the utility could be  found,
       but not invoked. Some scripts produce meaningful error messages differentiating the 126 and 127 cases. The dis-
       tinction between exit codes 126 and 127 is based on KornShell practice that uses 127 when all attempts to  exec
       the utility fail with [ENOENT], and uses 126 when any attempt to exec the utility fails for any other reason.

EXAMPLES
       It  is  frequently  desirable  to  apply  nohup  to pipelines or lists of commands. This can be done by placing
       pipelines and command lists in a single file; this file can then be invoked as a utility, and the nohup applies
       to everything in the file.

       Alternatively, the following command can be used to apply nohup to a complex command:


              nohup sh -c 'complex-command-line'

RATIONALE
       The  4.3  BSD version ignores SIGTERM and SIGHUP, and if ./nohup.out cannot be used, it fails instead of trying
       to use $HOME/nohup.out.

       The csh utility has a built-in version of nohup that acts differently from the nohup defined in this volume  of
       IEEE Std 1003.1-2001.

       The  term  utility is used, rather than command, to highlight the fact that shell compound commands, pipelines,
       special built-ins, and so on, cannot be used directly. However, utility includes user application programs  and
       shell scripts, not just the standard utilities.

       Historical versions of the nohup utility use default file creation semantics. Some more recent versions use the
       permissions specified here as an added security precaution.

       Some historical implementations ignore SIGQUIT in addition to SIGHUP; others ignore SIGTERM. An early  proposal
       allowed,  but  did not require, SIGQUIT to be ignored. Several reviewers objected that nohup should only modify
       the handling of SIGHUP as required by this volume of IEEE Std 1003.1-2001.

FUTURE DIRECTIONS
       None.

SEE ALSO
       Shell Command Language, sh, the System Interfaces volume of IEEE Std 1003.1-2001, signal()

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Stan-
       dard  for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifica-
       tions 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 Stan-
       dard, 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                            NOHUP(1P)