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 differ (con-
       sult 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 out-
       put 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 per-
       mission 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 precedence  of  international-
              ization 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 example, 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 written to stan-
              dard 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 exe-
       cution 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  standard  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 distinction between exit codes 126 and 127 is  based  on  Korn-
       Shell  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  permis-
       sions 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, Standard for
       Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6,  Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                     NOHUP(1P)