bash iterate file list, except when empty

Question

I thought this would be simple - but it is proving more complex than I expected.

I want to iterate through all the files of a particular type in a directory, so I write this:

#!/bin/bash for fname in *.zip ; do echo current file is ${fname} done 

This works as long as there is at least one matching file in the directory. However if there are no matching files, I get this:

current file is *.zip 

I then tried:

#!/bin/bash FILES=`ls *.zip` for fname in "${FILES}" ; do echo current file is ${fname} done 

While the body of the loop does not execute when there are no files, I get an error from ls:

ls: *.zip: No such file or directory 

How do I write a loop which cleanly handles no matching files?

Answer 1

In bash, you can set the nullglob option so that a pattern that matches nothing "disappears", rather than treated as a literal string:

shopt -s nullglob for fname in *.zip ; do echo "current file is ${fname}" done 

In POSIX shell script, you just verify that fname exists (and at the same time with [ -f ], check it is a regular file (or symlink to regular file) and not other types like directory/fifo/device...):

for fname in *.zip; do [ -f "$fname" ] || continue printf '%s\n' "current file is $fname" done 

Replace [ -f "$fname" ] with [ -e "$fname" ] || [ -L "$fname ] if you want to loop over all the (non-hidden) files whose name ends in .zip regardless of their type.

Replace *.zip with .*.zip .zip *.zip if you also want to consider hidden files whose name ends in .zip.

Answer 2

set ./* #set the arg array to glob results ${2+":"} [ -e "$1" ] && #if more than one result skip the stat "$1" printf "current file is %s\n" "$@" #print the whole array at once ###or### ${2+":"} [ -e "$1" ] && #same kind of test for fname #iterate singly on $fname var for array do printf "file is %s\n" "$fname" #print each $fname for each iteration done 

In a comment here you mention invoking a function...

file_fn() if [ -e "$1" ] || #check if first argument exists [ -L "$1" ] #or else if it is at least a broken link then for f #if so iterate on "$f" do : something w/ "$f" done else command <"${1-/dev/null}" #only fail w/ error if at least one arg fi file_fn * 

Answer 3

Use find

export -f myshellfunc find . -mindepth 1 -maxdepth 1 -type f -name '*.zip' -exec bash -c 'myshellfunc "$0"' {} \; 

You MUST export your shell function with export -f for this to work. Now find executes bash which executes your shell function, and remains at the current dir level only.

Answer 4

Instead of:

FILES=`ls *.zip` 

Try:

FILES=`ls * | grep *.zip` 

This way if ls fails (which it does in your case) it will grep the failed output and return as a blank variable.

current file is <---Blank Here 

You can add some logic to this to make it return "No File Found"

#!/bin/bash FILES=`ls * | grep *.zip` if [[ $? == "0" ]]; then for fname in "$FILES" ; do echo current file is $fname done else echo "No Files Found" fi 

This way if the previous command succeeded (exited with a 0 value) then it will print the current file, otherwise it would print "No Files Found"