Does nohup apply only to a child process of a shell process, but not to a child process of a non-shell process?

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nohup is an external program. How can it change the action of SIGHUP by a child process of a shell process to be "ignore"? (in terms of some arguments when the child process invokes fork() and/or execve() on the program which follows nohup?)



Does nohup apply only to a child process of a shell process, but not to a child process of a non-shell process?



Thanks.






nohup sighup







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  • nohup itself is the child process
    – frostschutz
    Nov 26 at 22:24















up vote
0
down vote

favorite












nohup is an external program. How can it change the action of SIGHUP by a child process of a shell process to be "ignore"? (in terms of some arguments when the child process invokes fork() and/or execve() on the program which follows nohup?)



Does nohup apply only to a child process of a shell process, but not to a child process of a non-shell process?



Thanks.






nohup sighup







share|improve this question























  • nohup itself is the child process
    – frostschutz
    Nov 26 at 22:24













up vote
0
down vote

favorite









up vote
0
down vote

favorite











nohup is an external program. How can it change the action of SIGHUP by a child process of a shell process to be "ignore"? (in terms of some arguments when the child process invokes fork() and/or execve() on the program which follows nohup?)



Does nohup apply only to a child process of a shell process, but not to a child process of a non-shell process?



Thanks.






nohup sighup







share|improve this question















nohup is an external program. How can it change the action of SIGHUP by a child process of a shell process to be "ignore"? (in terms of some arguments when the child process invokes fork() and/or execve() on the program which follows nohup?)



Does nohup apply only to a child process of a shell process, but not to a child process of a non-shell process?



Thanks.






nohup sighup




nohup sighup






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited Nov 26 at 21:49

























asked Nov 26 at 21:40









Tim

25.2k72243445




25.2k72243445











  • nohup itself is the child process
    – frostschutz
    Nov 26 at 22:24

















  • nohup itself is the child process
    – frostschutz
    Nov 26 at 22:24
















nohup itself is the child process
– frostschutz
Nov 26 at 22:24





nohup itself is the child process
– frostschutz
Nov 26 at 22:24











1 Answer
1






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oldest

votes

















up vote
3
down vote



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nohup configures itself to ignore the SIGHUP signal; see for example the GNU implementation. The POSIX specification for nohup states that




At the time the named utility is invoked, the SIGHUP signal shall be set to be ignored.




As also specified by POSIX, child processes inherit ignored signals other than SIGCHLD, so any process started by nohup after it’s ignored SIGHUP will itself ignore SIGHUP.



nohup’s handling applies to any child of nohup, regardless of nohup’s parent process. nohup does not (nor can it) affect the way signals are handled by any of its parents, whether they’re shells or not.






share|improve this answer






















  • Thanks. "child processes inherit ignored signals other than SIGCHLD, so any process started by nohup after it’s ignored SIGHUP will itself ignore SIGHUP." Is this specified as some argument to execve()?
    – Tim
    Nov 26 at 22:07











  • No, it’s how all the exec functions are specified, in all cases. There is no exec argument you can use to change that.
    – Stephen Kitt
    Nov 26 at 22:13










  • Is it that way only for implementing nohup?
    – Tim
    Nov 26 at 22:16










  • I suspect that nohup was taken into consideration when that part of POSIX was written, but it wasn’t the only consideration; see the rationale section on exec for details.
    – Stephen Kitt
    Nov 26 at 22:23










  • Thanks. Guru Stephen, may I call your attention to unix.stackexchange.com/questions/484344/…
    – Tim
    Nov 27 at 14:50










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1 Answer
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active

oldest

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1 Answer
1






active

oldest

votes









active

oldest

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active

oldest

votes








up vote
3
down vote



accepted










nohup configures itself to ignore the SIGHUP signal; see for example the GNU implementation. The POSIX specification for nohup states that




At the time the named utility is invoked, the SIGHUP signal shall be set to be ignored.




As also specified by POSIX, child processes inherit ignored signals other than SIGCHLD, so any process started by nohup after it’s ignored SIGHUP will itself ignore SIGHUP.



nohup’s handling applies to any child of nohup, regardless of nohup’s parent process. nohup does not (nor can it) affect the way signals are handled by any of its parents, whether they’re shells or not.






share|improve this answer






















  • Thanks. "child processes inherit ignored signals other than SIGCHLD, so any process started by nohup after it’s ignored SIGHUP will itself ignore SIGHUP." Is this specified as some argument to execve()?
    – Tim
    Nov 26 at 22:07











  • No, it’s how all the exec functions are specified, in all cases. There is no exec argument you can use to change that.
    – Stephen Kitt
    Nov 26 at 22:13










  • Is it that way only for implementing nohup?
    – Tim
    Nov 26 at 22:16










  • I suspect that nohup was taken into consideration when that part of POSIX was written, but it wasn’t the only consideration; see the rationale section on exec for details.
    – Stephen Kitt
    Nov 26 at 22:23










  • Thanks. Guru Stephen, may I call your attention to unix.stackexchange.com/questions/484344/…
    – Tim
    Nov 27 at 14:50














up vote
3
down vote



accepted










nohup configures itself to ignore the SIGHUP signal; see for example the GNU implementation. The POSIX specification for nohup states that




At the time the named utility is invoked, the SIGHUP signal shall be set to be ignored.




As also specified by POSIX, child processes inherit ignored signals other than SIGCHLD, so any process started by nohup after it’s ignored SIGHUP will itself ignore SIGHUP.



nohup’s handling applies to any child of nohup, regardless of nohup’s parent process. nohup does not (nor can it) affect the way signals are handled by any of its parents, whether they’re shells or not.






share|improve this answer






















  • Thanks. "child processes inherit ignored signals other than SIGCHLD, so any process started by nohup after it’s ignored SIGHUP will itself ignore SIGHUP." Is this specified as some argument to execve()?
    – Tim
    Nov 26 at 22:07











  • No, it’s how all the exec functions are specified, in all cases. There is no exec argument you can use to change that.
    – Stephen Kitt
    Nov 26 at 22:13










  • Is it that way only for implementing nohup?
    – Tim
    Nov 26 at 22:16










  • I suspect that nohup was taken into consideration when that part of POSIX was written, but it wasn’t the only consideration; see the rationale section on exec for details.
    – Stephen Kitt
    Nov 26 at 22:23










  • Thanks. Guru Stephen, may I call your attention to unix.stackexchange.com/questions/484344/…
    – Tim
    Nov 27 at 14:50












up vote
3
down vote



accepted







up vote
3
down vote



accepted






nohup configures itself to ignore the SIGHUP signal; see for example the GNU implementation. The POSIX specification for nohup states that




At the time the named utility is invoked, the SIGHUP signal shall be set to be ignored.




As also specified by POSIX, child processes inherit ignored signals other than SIGCHLD, so any process started by nohup after it’s ignored SIGHUP will itself ignore SIGHUP.



nohup’s handling applies to any child of nohup, regardless of nohup’s parent process. nohup does not (nor can it) affect the way signals are handled by any of its parents, whether they’re shells or not.






share|improve this answer














nohup configures itself to ignore the SIGHUP signal; see for example the GNU implementation. The POSIX specification for nohup states that




At the time the named utility is invoked, the SIGHUP signal shall be set to be ignored.




As also specified by POSIX, child processes inherit ignored signals other than SIGCHLD, so any process started by nohup after it’s ignored SIGHUP will itself ignore SIGHUP.



nohup’s handling applies to any child of nohup, regardless of nohup’s parent process. nohup does not (nor can it) affect the way signals are handled by any of its parents, whether they’re shells or not.







share|improve this answer














share|improve this answer



share|improve this answer








edited Nov 26 at 22:20

























answered Nov 26 at 21:57









Stephen Kitt

160k24357432




160k24357432











  • Thanks. "child processes inherit ignored signals other than SIGCHLD, so any process started by nohup after it’s ignored SIGHUP will itself ignore SIGHUP." Is this specified as some argument to execve()?
    – Tim
    Nov 26 at 22:07











  • No, it’s how all the exec functions are specified, in all cases. There is no exec argument you can use to change that.
    – Stephen Kitt
    Nov 26 at 22:13










  • Is it that way only for implementing nohup?
    – Tim
    Nov 26 at 22:16










  • I suspect that nohup was taken into consideration when that part of POSIX was written, but it wasn’t the only consideration; see the rationale section on exec for details.
    – Stephen Kitt
    Nov 26 at 22:23










  • Thanks. Guru Stephen, may I call your attention to unix.stackexchange.com/questions/484344/…
    – Tim
    Nov 27 at 14:50
















  • Thanks. "child processes inherit ignored signals other than SIGCHLD, so any process started by nohup after it’s ignored SIGHUP will itself ignore SIGHUP." Is this specified as some argument to execve()?
    – Tim
    Nov 26 at 22:07











  • No, it’s how all the exec functions are specified, in all cases. There is no exec argument you can use to change that.
    – Stephen Kitt
    Nov 26 at 22:13










  • Is it that way only for implementing nohup?
    – Tim
    Nov 26 at 22:16










  • I suspect that nohup was taken into consideration when that part of POSIX was written, but it wasn’t the only consideration; see the rationale section on exec for details.
    – Stephen Kitt
    Nov 26 at 22:23










  • Thanks. Guru Stephen, may I call your attention to unix.stackexchange.com/questions/484344/…
    – Tim
    Nov 27 at 14:50















Thanks. "child processes inherit ignored signals other than SIGCHLD, so any process started by nohup after it’s ignored SIGHUP will itself ignore SIGHUP." Is this specified as some argument to execve()?
– Tim
Nov 26 at 22:07





Thanks. "child processes inherit ignored signals other than SIGCHLD, so any process started by nohup after it’s ignored SIGHUP will itself ignore SIGHUP." Is this specified as some argument to execve()?
– Tim
Nov 26 at 22:07













No, it’s how all the exec functions are specified, in all cases. There is no exec argument you can use to change that.
– Stephen Kitt
Nov 26 at 22:13




No, it’s how all the exec functions are specified, in all cases. There is no exec argument you can use to change that.
– Stephen Kitt
Nov 26 at 22:13












Is it that way only for implementing nohup?
– Tim
Nov 26 at 22:16




Is it that way only for implementing nohup?
– Tim
Nov 26 at 22:16












I suspect that nohup was taken into consideration when that part of POSIX was written, but it wasn’t the only consideration; see the rationale section on exec for details.
– Stephen Kitt
Nov 26 at 22:23




I suspect that nohup was taken into consideration when that part of POSIX was written, but it wasn’t the only consideration; see the rationale section on exec for details.
– Stephen Kitt
Nov 26 at 22:23












Thanks. Guru Stephen, may I call your attention to unix.stackexchange.com/questions/484344/…
– Tim
Nov 27 at 14:50




Thanks. Guru Stephen, may I call your attention to unix.stackexchange.com/questions/484344/…
– Tim
Nov 27 at 14:50

















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