bash loop through two Directories

Question

I try to loop through two directories and echo all files with a given extension with this script:

#!/bin/bash
FOLDERS=/sdd/DATA/ /sdc/storage/
for d in $FOLDERS; do
echo "$d"
  FILES=$d*.txt
  for f in $FILES; do
    echo "$f"
  done
done

but I do not get this script to work! I get bash: sdc/storage/ is a directory

I would expect you to get an error like -bash: /sdc/storage: is a directory — William Pursell
– William Pursell, Commented Aug 27, 2019 at 21:59
...which can be fixed by enclosing /sdd/DATA/ /sdc/storage/ in quotation marks. (Without, that line sets FOLDERS=/sdd/DATA/ and then attempts to execute /sdc/storage/, which doesn't work because -- guess what -- it's a directory. ;-) ) Even better would be to be aware of filenames with spaces in them, and either doing "the IFS thing" with for ... in ..., or using find ... -exec .... — DevSolar
– DevSolar, Commented Aug 27, 2019 at 22:01
@DevSolar, ...*could* be fixed that way, but it'd be very bad practice to define FOLDERS as a string rather than an array. Aiming for the most obvious issue first, it'd break the moment you had a directory name with spaces. — Charles Duffy
– Charles Duffy, Commented Aug 27, 2019 at 22:11

Charles Duffy · Accepted Answer · 2019-08-27 22:12:07Z

4

Doing this right would look like:

#!/bin/bash
folders=( /sdd/DATA/ /sdc/storage/ )
for d in "${folders[@]}"; do
  echo "$d"
  files=( "$d"*.txt )
  printf '%s\n' "${files[@]}" # print the files array, one per line
done

Note:

array=( "first item" "second item" ) defines a two-item array; "${array[@]}" expands to those items.
When expanding an element, we want to quote the parts the shell shouldn't string-split or glob-expand, but leave any glob patterns unquoted; thus, "$d"*.txt.
We're using lowercase names for user-defined variables. This is per POSIX-defined recommendation, which specify all-caps names as used for variables meaningful to the operating system and shell, whereas all other names are reserved for application use.

answered Aug 27, 2019 at 22:12

Charles Duffy

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