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Editorial Team
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Asked: 2026-05-30T21:29:14+00:00

What is the best solution to get values known in shell into the C

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What is the best solution to get values known in shell into the C binary application during its run-time?

The C application communicates with third party product and sends it actual settings.
But some settings are changed directly in OS, so I want to use some command from shell to influence, change, these variables in C application.

Do you know some way for achieving it (using variable, pipes, or maybe something differently other)?

I looked at global variables, but even though I change global variable value, it has no effect in C application which was running all time. (I used function getenv()).

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1 Answer

  1. Editorial Team

    Most long running processes (aka. daemon) in Unix have some kind of configuration files (e.g. /etc/mydaemon.conf) which they read (and evaluate)

    • at startup (of course)
    • when they receive a HUP signal.

    So the most easiest and well-known way is to install a signal handler in the C app and catch SIGHUP signals. This of course requires changes to the C app.

    To trigger a reread in the shell you can use one of these commands:

    kill -HUP PID_OF_MY_PROCESS
pkill -HUP name_of_my_process
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