bash.md

bash

finding proc by script name

script ./testX.bash

#!/bin/bash

countProc=$(pstree -pal -N user | grep testX | grep -v grep | wc -l)
#countProc=$(pgrep autoscaler --count)
echo $countProc
sleep 1000

execution

./testX.bash
2

bash ./testX.bash
2

If the subshell contains a pipeline then we get the forked copy of the script waiting for the pipeline to finish Without hashbang finding the proc by script name may not be possible

subshells and pipelines

Example of forking shell for pipielines

$ echo $$ $BASHPID | cat -
11656 31528
$ echo $$ $BASHPID
11656 11656
$ echo $$ | while read line; do echo $line $$ $BASHPID; done
11656 11656 31497
$ while read line; do echo $line $$ $BASHPID; done <<< $$
11656 11656 11656

running multiple processes

Handling two processes in a nice way:

prog1 & prog2 && fg

This will:

• start prog1.
• send it to background, but keep printing its output.
• start prog2, and keep it in foreground, so you can close it with ctrl-c.
• when you close prog2, you'll return to prog1's foreground, so you can also close it with ctrl-c.

The above is the same as

prog1 & prog2

There are more possible combinations like e.g.

prog1 & prog2 & prog 3