Linux › Section K · Shell scripts › Topic K.3
Conditionals
Scripts earn their keep by making decisions: skip a file that is missing, refuse a bad option, act only when a pattern is found. In the shell every decision rests on one thing, the exit code of a command, and once you see that, if, test and case stop being mysterious.
In this topic
- Decisions run on exit codes
- The [ command
- Worked example: the missing argument bug
- Any command can be a test
- elif: more than two branches
- File tests
- String and number tests
- Worked example: a case dispatcher
- bash extras: [[ ]] and (( ))
- Common mistakes to avoid
- Key takeaways
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