I’m always forgetting the syntax to make “for” loops in Bash. I guess it serves me right for using foreach most of my UNIX life instead. Anyhow, I know I will have to come back here to find it, so I thought I would write put up this quick example with the hope that it will be useful to others as well.
for i in $(seq 1 100); do echo -n "file${i} "; touch file${i} 2>&1; done
The the above for loop will create 100 files (called file1, file2, etc.).
This entry was posted on Monday, July 23rd, 2007 at 3:45 pm and is filed under Data and Technology.
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Thank you! I just love it when people leave little blog entries like this one. You saved me 5 or 10 minutes looking up in the bash manual how to do this.
I agree with Todd!
Thank you very much!
Nice one!
Was useful to me, thanks!
Thanks very much! Never would have figured seq 1 10 needed to be $(seq 1 10)!!:)
Agreed, Thanks for posting.
Thanks for this, I couldn’t find anywhere how to generate n numbers, seq worked like a charm.
How about “touch file{1..100}” as an easier solution using bash.
Thank you very much for the code.
Nice and helpful..
Cheers!
Haha, took a look at a couple of website just before happening upon yours. There’s no way I would have been able to figure this one out so quickly (if at all) if it hadn’t have been for your great blurb on the subject here. Thanks.
What about:
for (( i=1;i&1; done
I guess for huge loops like 1000 or 100 000 this might work better.
Sorry my code was messed up in my previous comment. Hopefully it is OK this time:
for (( i=1;i<=100;i+=1 )) ; do echo -n "file${i} "; touch file${i} 2>&1; done
kobit why double parenthesis is needed?
eloy: you can found a answer here :
http://www.linuxtopia.org/online_books/advanced_bash_scripting_guide/dblparens.html
so accully you can use a C-style in double parenthesis
P.S.: Google is your friend
ei thanks! very useful!
How I can write loop without nubmers but with some strings like ‘a’, ‘b’, ‘c’?
Just came across this, but just for completeness:
Regarding using strings instead of numbers:
touch file{a..c}
or
for i in {a..c}; do something…; done
or
{‘a’,'b’,'c’,'etc’}
None of these work with solaris 5.8 bash…it doesnt have seq and i cant figure it out…VERY frustrating
This example parsing the output of seq to an array is considered very bad practice. seq is a non-standard unix/linux program and often isn’t included in many distros.
The proper technique is to use either for-in as an iterator, or to use c-style looping as was mentioned in a few comments.
Dan,
Not arguing your point, but the purpose of this was never to provide the world with a script that creates numbered files. The only real point was to help me remember how to do something for each line of output from some random program. What can I say, I have a bad memory.
Can you provide a script that would read a text file list of companies, and batch create individual text files for each company? TIA!
Never mind, I just converted my list to a comma-separated list and used…
touch {‘comma’,'separated’,'list’}.txt
more of a lambda approach
seq 1 100|while read i; do echo -n “file${i} “; touch file${i} 2>&1; done
with letters you can
cat<<EOF|while read line; do echo -n “file$line “; touch file$line; done
first line
second line
another
another
EOF
or create a file delimited by new lines
cat thefile|while read line; do echo -n “file$line “; touch file$line; done
Hi,
When i executed ” for (( i=1;i&1; ”
I got an error like: ” ./forloop.ksh[3]: syntax error at line 3 : `((‘ unexpected ”
Request you to please provide me a solution for FOR LOOP with range like in C.
Regards
Balaji K
Hi,
I got solution fro the above, i ran that in ksh, now i ran that under bash, now it is working fine.
For Loop in bash, pls browse:
http://tldp.org/LDP/abs/html/loops1.html
Regards
Balaji K
seq is very helpful. A related post
http://unstableme.blogspot.com/2008/12/ways-of-writing-bash-for-loop.html
thanks a lot !!!!