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

       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.

       nohup — invoke a utility immune to hangups

       nohup utility [argument...]

       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 vari‐
       able. 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.


       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  Sec‐
		 tion  2.14, Special Built-In Utilities, the results are unde‐

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

       Not used.


       The  following  environment  variables  shall  affect  the execution of

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

       LANG	 Provide  a  default  value for the internationalization vari‐
		 ables that are unset or null. (See the Base Definitions  vol‐
		 ume  of POSIX.1‐2008, Section 8.2, Internationalization Vari‐
		 ables 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).

		 Determine the locale that should be used to affect the format
		 and  contents	of  diagnostic	messages  written  to standard

       NLSPATH	 Determine the location of message catalogs for the processing

       PATH	 Determine  the search path that is used to locate the utility
		 to  be	 invoked.  See	the   Base   Definitions   volume   of
		 POSIX.1‐2008, Chapter 8, Environment Variables.

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

       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.

       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

       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


       The following exit values shall be returned:

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

       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 speci‐
       fied by the utility operand.


       The following sections are informative.

       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 val‐
       ues 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 differ‐
       entiating 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.

       It is frequently desirable to apply nohup to pipelines or lists of com‐
       mands. 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

       The 4.3 BSD version ignores SIGTERM and SIGHUP, and if ./nohup.out can‐
       not 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.1‐2008.

       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

       Historical versions of nohup did not affect standard  input,  but  that
       causes  problems in the common scenario where the user logs into a sys‐
       tem, 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 &


       Chapter 2, Shell Command Language, sh

       The Base Definitions volume of  POSIX.1‐2008,  Chapter  8,  Environment

       The System Interfaces volume of POSIX.1‐2008, signal()

       Portions	 of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       --  Portable  Operating	System	Interface (POSIX), The Open Group Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
       cal  and	 Electronics  Engineers,  Inc  and  The	 Open Group.  (This is
       POSIX.1-2008 with the 2013 Technical Corrigendum	 1  applied.)  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 .

       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.ker‐ .

IEEE/The Open Group		     2013			     NOHUP(1P)

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