Shell script nested loop

Question

I want to produce a list of files between 14 and 22 April.
The filenames will have the date in the name, e.g. J0018658.WANCL90A.16Apr2014.214001.STD.txt.
I have tried this script.

for i in 14 15 16 17 18 19 20 21 22; do
    for x in *$iApr*.txt; do
      echo "$x"
    done
done

I am using this on AIX and the default shell is ksh. However sh and bash are also available. Here is what works with ksh:

for i in 14 15 16 17 18 19 20 21 22; do
    for x in *${i}Apr*.txt; do
        echo "$x"
    done
done

Here is what works even better with bash:

#!/bin/bash

shopt -s nullglob
for i in {14..22}; do
    for x in *${i}Apr*.txt; do
          echo "$x"
    done
done

Digital Trauma · Accepted Answer · 2014-04-23 19:42:54Z

3

bash will try to expand a variable called iApr, which is not what you want.

Instead, try making your inner for loop look like this:

for x in *${i}Apr*.txt; do

Also, your outer loop can be similar to the concept in @anubhava's answer:

for i in {14..22}; do

So the script should look something like this:

#!/bin/bash

shopt -s nullglob
for i in {14..22}; do
    for x in *${i}Apr*.txt; do
          echo "$x"
    done
done

Again, thanks @anubhava for pointing out the necessity of shopt -s nullglob

About #!/bin/sh vs. #!/bin/bash:

If you're running Linux, your /bin/sh is likely simply a symlink to /bin/bash. From the man page:

If bash is invoked with the name sh, it tries to mimic the startup behavior of historical versions of sh as closely as possible, while conforming to the POSIX standard as well.

edited Apr 23, 2014 at 19:42

answered Apr 23, 2014 at 16:46

Digital Trauma

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5 Comments

Brian G Over a year ago

Script now looks like:for i in {14..22}; do for x in *${i}Apr*.txt; do echo "$x" done done However the output is just *{14..22}Apr*.txt done

Digital Trauma Over a year ago

Which version of bash are you using? Do you have !#/bin/bash or #!/bin/sh at the top of the script? You'll need at least version 3.2 and !#/bin/bash to do the {14..22} expansion.

Brian G Over a year ago

I guess my sh is too old. I switched to /bin/bash and it works. Thanks

Digital Trauma Over a year ago

@BrianG see my note about #!/bin/sh vs. #!/bin/bash

Brian G Over a year ago

Thanks for the info about sh vs bash. I am actually using AIX and the default shell is ksh, but sh and bash are both available.

anubhava · Accepted Answer · 2014-04-23 16:48:12Z

2

You can do:

ls *{14..22}Apr*.txt

OR in BASH:

shopt -s nullglob; echo *{14..22}Apr*.txt

answered Apr 23, 2014 at 16:48

anubhava

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