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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  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 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 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
       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
       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()

       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 .