Bash shell script for 100 iterations and log time taken

Question

How do I run 100 iterations using a bash shell script? I want to know how long it will take to execute one command (start and end time). I want to keep track which iteratio

Answer 1

You can try with:

for i in {1..100}; do time some_script.sh; done 2>&1 | grep ^real | sed -e s/.*m// | awk '{sum += $1} END {print sum / NR}'

Explanation

• The for loop runs some_script.sh 100 times, measuring its execution time with time
• The stderr of the for loop is redirected to stdout, this is to capture the output of time so we can grep it
• grep ^real is to get only the lines starting with "real" in the output of time
• sed is to delete the beginning of the line up to minutes part (in the output of time)
• For each line, awk adds to the sum, so that in the end it can output the average, which is the total sum, divided by the number of input records (= NR)

Limitations

The snippet assumes that the running time of some_script.sh is less than 1 minute, otherwise it won't work at all. Depending on your system, the time builtin might work differently. Another alternative is to use the time command /usr/bin/time instead of the bash builtin.

Note: This script was extracted from here.