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

-1

By: dennisw

2009-09-18 02:51:12

echo bash strings

2 Alternatives + Submit Alt

for loop with leading zero in bash 3
This is sample output - yours may be different.
5

seq -s " " -w 3 20

edo · 2009-09-19 21:26:57 7
for loop with leading zero in bash 3

emulates bash4's "echo {03..20}" Uses bash3 builtin function printf Show Sample Output
This is sample output - yours may be different.
```
03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20
```
0

printf "%02u " {3..20}; echo

Escher · 2009-09-18 18:48:41 4

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 · 785 weeks and 4 days 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 · 785 weeks and 3 days ago

rahimhh21 · 109 weeks and 2 days ago

Perfecthomepugs · 100 weeks and 6 days ago

pugpuppies95 · 63 weeks 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?

You must be signed in to comment.

What's this?

commandlinefu.com is the place to record those command-line gems that you return to again and again. That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and voted up or down.

Share Your Commands

Similar Commands

Copy something to multiple SSH hosts with a Bash loop

shell bash iterate number range with for loop

bash function to check for something every 5 seconds

Mixing music in bash

Stay in the loop…

Follow the Tweets.

Every new command is wrapped in a tweet and posted to Twitter. Following the stream is a great way of staying abreast of the latest commands. For the more discerning, there are Twitter accounts for commands that get a minimum of 3 and 10 votes - that way only the great commands get tweeted.

» http://twitter.com/commandlinefu
» http://twitter.com/commandlinefu3
» http://twitter.com/commandlinefu10

Subscribe to the feeds.

Use your favourite RSS aggregator to stay in touch with the latest commands. There are feeds mirroring the 3 Twitter streams as well as for virtually every other subset (users, tags, functions,…):

Subscribe to the feed for:

» all commands
» commands with 3 up-votes (commandlinefu3)
» commands with 10 up-votes (commandlinefu10)