for loop with leading zero in bash 3

printf "%02u " {3..20}; echo
emulates bash4's "echo {03..20}" Uses bash3 builtin function printf
Sample Output
03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20

By: Escher
2009-09-18 18:48:41

2 Alternatives + Submit Alt

  • 5
    seq -s " " -w 3 20
    edo · 2009-09-19 21:26:57 2
  • 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} Show Sample Output

    for i in {0..1}{0..9}; do echo $i; done
    dennisw · 2009-09-18 02:51:12 2

What Others Think

If you allow non-builtins to generate the numbers, then the seq command (part of gnu coreutils) may also do this with "seq -w 19": for n in $(seq -w 19); do ... ; done seq supports a printf-style format string as well. On freeBSD, seq->jot.
bwoodacre · 631 weeks and 3 days 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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