How Much Do Echo Statements Slow Down a Bash Script?

Software-Dev

Jul, 27 2020

Contents

Goal

I was trying to optimize a bash script and wondered how much echo statements would slow it down, so I did a few tests. I was specifically wondering if adding a check for verbosity before an echo statement would have a significant affect on runtime, vs just removing the echo statement all together.

Script

I used this script to run the benchmark:

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export TIMEFORMAT=%R	
verbose=1	
echo=foo	
echo=01234567890123456789012345678901234567890123456789	
for i in {1..10}; do	
	time (for i in {1..1000000}; do [[ verbose -eq 1 ]] && echo $echo; done > /tmp/file.log) 2>> foocheckTrue.log
	time (for i in {1..1000000}; do [[ verbose -eq 0 ]] && echo $echo; done > /tmp/file.log) 2>> foocheckFalse.log
	time (for i in {1..1000000}; do echo $echo; done > /tmp/file.log) 2>> foonoCheck.log
	time (for i in {1..1000000}; do : ; done) 2>> foonoPrint.log
done	

I set echo to 01234567890123456789012345678901234567890123456789 when benchmarking for long echo statements, and to foo when benchmarking short echo statements.

Results

Long Echo Statement

Trial	Don’t check for verbosity and don’t print	Check for verbosity and don’t print	Don’t check for verbosity and print	Check for verbosity and print
1	1.505	2.232	4.048	5.642
2	1.461	2.258	4.056	5.496
3	1.531	2.27	4.166	5.481
4	1.531	2.31	4.187	5.508
4	1.522	4.11	4.188	7.195
5	1.83	3.532	5.29	6.008
6	1.9	3.262	6.116	6.696
7	1.795	2.669	4.901	7.356
8	1.835	2.454	4.163	6.418
9	1.536	2.946	4.555	6.636
Average	1.6446	2.8043	4.567	6.2436

Short Echo Statement

Trial	Don’t check for verbosity and don’t print	Check for verbosity and don’t print	Don’t check for verbosity and print	Check for verbosity and print
1	1.471	2.229	2.909	4.464
2	1.481	2.233	3.001	4.602
3	1.496	2.236	2.94	4.433
4	1.473	2.226	2.994	4.682
4	1.477	2.275	2.892	4.368
5	1.537	2.333	3.275	4.547
6	1.559	2.244	2.931	4.493
7	1.507	2.184	2.961	4.475
8	1.468	2.185	2.864	4.37
9	1.483	2.204	2.864	4.357
Average	1.4952	2.2349	2.9631	4.4791

Conclusion

The different options had significant differences in runtime. Checking for verbosity and not printing took an average of 1.5 - 1.7 times as long as not printing anything at all! I definitely took this into consideration when deciding which echo statements were really necessary for my bash script.

It’s worth noting that this benchmark is based on echoing to a file. By echoing to the console the options that print would take significantly longer.

Let me know if you have any comments below!