Modify environment variables of a running process

Use GDB to attach to the process

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# gdb -p <Process-PID>

Set environment variable

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(gdb) p setenv("Key", "Value")

Exit

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(gdb) q

Sample C Program

​x
/*
 * setlive_env.c
 */
#include <stdlib.h>
#include <stdio.h>
​
int
main(int argc, char *argv[])
{
        int     i = 0;
        char    *env_val;
​
        for (i = 0; i < 10; i++) {
                env_val = getenv("Env_Key");
                printf("Env Val for TZ: %s\n", env_val);
                sleep(5);
        }
​
        return (0);
}

Build the code:

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# gcc setenv_live.c -o setenv_live.o

Run the code:

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# ./setenv_live.o

Initial Output:

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# ./setenv_live.o
Env Val for TZ: (null)
Env Val for TZ: (null)

Run gdb to attach to the process

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# gdb -p <PID-OF-ABOVE-PROCESS>

Set env value and exit

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(gdb) p setenv("Env_Key", "New_Value")
$1 = 0
(gdb) q
A debugging session is active.
​
        Inferior 1 [process 11414] will be detached.
​
Quit anyway? (y or n) y
Detaching from program: /root/setenv_live.o, process 11414

Output after setting env variable:

# ./setenv_live.o
Env Val for TZ: (null)
Env Val for TZ: (null)
Env Val for TZ: New_Value
Env Val for TZ: New_Value
Env Val for TZ: New_Value
Env Val for TZ: New_Value
Env Val for TZ: New_Value
Env Val for TZ: New_Value
Env Val for TZ: New_Value
Env Val for TZ: New_Value