Linux Basic — Optimizing Scripts
Optimizing Scripts
Bash is interpreted and fork-heavy. Small inefficiencies compound in loops. This chapter shows you where the bottlenecks are and how to fix them without rewriting in Python.
What You Will Learn
By the end of this chapter you will be able to:
- Identify and avoid unnecessary forking (subshells, external commands)
- Choose builtins over external commands where possible
- Understand array vs string performance trade-offs
- Profile scripts with
timeand identify hotspots - Parallelise work with xargs and GNU Parallel
Topics in This Chapter
| # | Topic | Description |
|---|---|---|
| 1 | Avoid Unnecessary Forking | subshells, backticks, pipes |
| 2 | Builtins vs External | [[ vs [, printf vs echo |
| 3 | Array vs String Performance | when arrays are faster |
| 4 | Profiling with time | real vs user vs sys, per-line timing |
| 5 | xargs & GNU Parallel | parallelise command batches |
| 6 | Practice Exercises | Hands-on tasks |
When to Optimise
Premature optimisation is the root of all evil. Measure first:
- Does the script take > 5 seconds?
- Does it run in a loop or cron job (frequency multiplies cost)?
- Is the slowness user-facing?
If yes to 2 or 3, profile and optimise. Otherwise, focus on readability.
The 80/20 Rule
In most scripts, 80% of runtime comes from:
- External commands (
grep,sed,awk) in tight loops - Unnecessary subshells
- Serial processing of parallelisable work
Fix those three and you’ll see 10×+ speedups.
Next → Avoid Unnecessary Forking
