What Shells Do (cont)
The "transformations" applied to input lines include:
- history substitution ... e.g.
!20 !awk
- file name expansion ... e.g.
*.c enr.07s?
- variable evaluation ... e.g.
$PWD ${x-20}
To "execute that command" the shell needs to:
- find file containing named program (
PATH)
- start new process for execution of program
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