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I use nohup quite often for important long running processes under linux/bash, so much so that nohup time my command with arguments && mv nohup.out my.log is almost an idiom for me.

The problem is that nohup puts both stdout and stderr into nohup.out, and I cannot control the name of the file. This means that if I accidentally start two nohups in the same directory, their output will be interleaved in nohup.out.

The questions are:

  1. How do I deal with this problem? Always running nohups in separate directories and writing a shell function which will first check for ./nohup.out are two sucky options I see.

  2. How come I cannot tell nohup.out where to redirect the output? GNU tools tend to have so many options, why not nohup?

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2 Answers 2

You can redirect both stdout and stderr to one file. With Bash 4 (or others such as Zsh), as easy as:

nohup <some-command> &> output.log

I can't tell you why there's no separate option for nohup to set the output, but if your shell can take care of that, you don't really need an option.

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Will it prevent nohup from performing its own redirection? –  grawity Feb 14 '13 at 15:45
1  
GNU nohup says that it'll redirect stdout to a file if you specify nohup command > file. BSD nohup doesn't mention this at all, but it worked for me. –  slhck Feb 14 '13 at 15:50

There are more ways than just nohup to start a process so that it would ignore SIGHUP; for example: (written as shell functions)

nohup() {
    setsid "$@"
}

nohup() {
    ("$@" &)
}

nohup() {
    "$@" & disown
}

(setsid, or even (setsid "$@" &), might be the best choice.)

All of them allow you to specify your own redirections with >, 2>, and &>/>&.

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