for loop with leading zero in bash 3

for i in {0..1}{0..9}; do echo $i; done
Bash 4 will let you do {00..19} to get leading zeros, but Bash 3 doesn't have that feature. This technique gets you partway there (the sequences need be such that the last digit ranges from zero to nine - you can't use this for something like Bash 4's {03..27}, for example). When this limitation is not a problem, you can avoid some complicated string manipulation for concatenating leading zeros. You can add more digits like this: {0..1}{0..9}{0..9} (ranges from 0 to 99 with up to two leading zeros). To pad with additional zeros: for i in 000{0..1}{0..9}; do echo $i; done or for i in {0..1}{0..9}; do echo "000$i"; done This is useful for creating values to sort or for creating filenames with a fixed format. Note that this will also work: touch {0..1}{0..9}
Sample Output

By: dennisw
2009-09-18 02:51:12

2 Alternatives + Submit Alt

What Others Think

I think we can obtain the same result using printf SIZE=2; BEGIN=0; END=19; CHAR='0'; for i in {${BEGIN}..${END}}; do printf "%${SIZE}i\n" ${i} | tr ' ' ${CHAR}; done
Gentux · 644 weeks and 1 day ago
@Gentux: Bash won't nest this way: {${BEGIN}..${END}}. Besides, using printf or var=0000$num; var=${var: -4} is the kind of "complicated string manipulation" I was referring to (although I rather like that last one - note that the space is required between the colon and the minus sign).
dennisw · 644 weeks and 1 day ago

What do you think?

Any thoughts on this command? Does it work on your machine? Can you do the same thing with only 14 characters?

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