Question

How to run the first process from a list of processes stored in a file and immediately delete the first line as if the file was a queue and I called ‘pop’?

I’d like to call the first command listed in a simple text file with \n as the separator in a pop-like fashion:

Figure 1:

cmdqueue.lst :  proc_C1 proc_C2 proc_C3 . . 

Figure 2:

Pop the first command via popcmd:

proc_A | proc_B | popcmd cmdqueue.lst | proc_D 

Figure 3:

cmdqueue.lst :  proc_C2 proc_C3 proc_C4 . . 

Answer 1

pop-cmd.py:

#!/usr/bin/env python import os, shlex, sys from subprocess import call filename = sys.argv[1] lines = open(filename).readlines() if lines:     command = lines[0].rstrip()     open(filename, 'w').writelines(lines[1:])     if command:         sys.exit(call(shlex.split(command) + sys.argv[2:])) 

Example:

proc_A | proc_B | python pop-cmd.py cmdstack.lst | proc_D