Stop using seq in Bash scripts

In the past, I used to generate sequences of numbers using the seq utility, for example:

$ seq 1 5
1
2
3
4
5

However, this is not recommended. seq may not exist on all systems, and there is a portable way to do this in Bash:

for i in {1..5}; do echo $i; done

However, this won’t work if the range parameters are in variables. In that case you can use this kind of loop:

max=5
for ((i=1; i<=$max; ++i)); do echo $i; done

More examples emulating seq using more portable methods:

# seq 1 2 10
for i in {1..10..2}; do echo $i; done
for ((i=1; i<=10; i+=2)); do echo $i; done

# seq -w 5 10
for ((i=5; i<=10; ++i)); do printf '%02d\n' $i; done

Stop using seq in Bash scripts —04 November 2014