Question

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What does $$ mean in the shell?

$ ./cruncher & ./cruncher & ./cruncher &
$ ps -C cruncher -p $$ -o pid,state,cmd
PID S CMD
2588 S bash
2657 R /bin/sh ./cruncher
2658 R /bin/sh ./cruncher
2659 R /bin/sh ./cruncher

-C cmdlist      Select by command name.
                       This selects the processes whose executable name is
                       given in cmdlist.

-p pidlist      Select by PID.
                       This selects the processes whose process ID numbers
                       appear in pidlist.

Question> What is the meaning of $$?

Answer 1

It has nothing to do with the ps command, $$ is substituted by the shell with its process ID.