PROLOG

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of this interface
       may differ (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  standard  input  is associated with a terminal, the nohup utility may redirect standard input from an
       unspecified file.

       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 standard error is a terminal and standard output is open but is not a terminal, all output written  by
       the  named  utility  to  its  standard error shall be redirected to the same open file description as the
       standard output. If standard error is a terminal and standard output either is a terminal or  is  closed,
       the same output shall instead be appended to the end of the nohup.out file as described above.

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 Section 2.14, 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 POSIX.1‐2017, 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 POSIX.1‐2017, 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

       Output written by the named utility is appended to  the  file  nohup.out  (or  $HOME/nohup.out),  if  the
       conditions hold as described in the DESCRIPTION.

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' </dev/null

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 POSIX.1‐2017.

       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 POSIX.1‐2017.

       Historical versions of nohup did not affect standard input,  but  that  causes  problems  in  the  common
       scenario where the user logs into a system, types the command:

           nohup make &

       at  the  prompt, and then logs out. If standard input is not affected by nohup, the login session may not
       terminate for quite some time, since standard input remains open until make exits. To avoid this problem,
       POSIX.1‐2008 allows implementations to redirect standard input if it is a terminal. Since the behavior is
       implementation-defined, portable applications that may run into  the  problem  should  redirect  standard
       input themselves. For example, instead of:

           nohup make &

       an application can invoke:

           nohup make </dev/null &

FUTURE DIRECTIONS

       None.

SEE ALSO

       Chapter 2, Shell Command Language, sh

       The Base Definitions volume of POSIX.1‐2017, Chapter 8, Environment Variables

       The System Interfaces volume of POSIX.1‐2017, signal()

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
       for  Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       Any typographical or formatting errors that appear in this page are most likely to have  been  introduced
       during   the   conversion  of  the  source  files  to  man  page  format.  To  report  such  errors,  see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                                   2017                                         NOHUP(1POSIX)