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Linux 2.6 - man page for nohup (linux section 1posix)

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

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 stan-
       dard 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  stan-
       dard 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 direc-
	      tory 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, Inter-
	      nationalization Variables for the precedence 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 interna-
	      tionalization 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 argu-
	      ments).

       LC_MESSAGES
	      Determine the locale that should be used to affect the format and contents of diag-
	      nostic messages written 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 stan-
       dard output generated by the execution of the utility specified by  the	operands.  Other-
       wise, 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 stan-
       dard 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  util-
       ity"  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 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, util-
       ity 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,  sig-
       nal()

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 orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003					 NOHUP(P)


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