if-then statement and wildcard: shell script

Cyberman · 12-26-2009, 12:22 AM

I have a bunch of .pdf files in a folder.
And if the folder already has .pdf files, then I simply want the file to meow. Otherwise, if it doesn't think .pdf files already exist, then go bark.

There are .pdf files in the folder.

Code:

#!/bin/sh
if [ -e ./*.pdf ]
then
echo "meow"
else
echo "bark"
fi

Quote:

./test: line 2: [: too many arguments
bark

How do I get it to go meow with a wildcard or something similar?

ghostdog74 · 12-26-2009, 12:25 AM

you don't have to do it that way (and its not the right way anyway)

Code:

shopt -s nullglob
for file in *.pdf
do
   if [ -f "$file" ];
     echo "bark"
   fi
done

jlinkels · 12-26-2009, 08:25 AM

Try something like this:

Code:

nrfiles=$(find . -maxdepth 1 -name "*.pdf" | wc -l)
if [ $nrfiles -gt 0 ]
then
  meow
else
  bark
fi

The problem with a construct like [ -e *.pdf ] is that the shell actually expands the token *.pdf to foo.pdf, bar.pdf... before it evaluates the expression. So the expression becomes

Code:

if [ -e foo.pdf bar.pdf baz.pdf ]

which is invalid of course.

jlinkels

ghostdog74 · 12-26-2009, 09:25 AM

Quote:

Originally Posted by jlinkels

Try something like this:

Code:

nrfiles=$(find . -maxdepth 1 -name "*.pdf" | wc -l)

another way, w/o external commands.

Code:

[ ! -z "$(echo *pdf)" ] && echo "meow"

jlinkels · 12-26-2009, 11:08 AM

Quote:

Originally Posted by ghostdog74

Code:

[ ! -z "$(echo *pdf)" ] && echo "meow"

If there are no pdf files present, the result of *pdf is "*pdf". At least in Bash this is true. Therefor the test file never yields false.

For the same reason you cannot use

Code:

for fname in $(ls *pdf)

as when no files are found ls produces an error string.

I have to admit that "echo *pdf" to get a listing of pdf files in the current directory is cool.

jlinkels

catkin · 12-26-2009, 12:11 PM

Quote:

Originally Posted by jlinkels

If there are no pdf files present, the result of *pdf is "*pdf". At least in Bash this is true. Therefor the test file never yields false.

For the same reason you cannot use

Code:

for fname in $(ls *pdf)

as when no files are found ls produces an error string.

Unless you use shopt -o nullglob in which case echo *pdf produces a single line-end and ls *pdf produces a listing of the current directory.

ghostdog74 · 12-26-2009, 05:17 PM

Quote:

Originally Posted by jlinkels

If there are no pdf files present, the result of *pdf is "*pdf". At least in Bash this is true. Therefor the test file never yields false.

i had my nullglob turned on by default so i didn't include. yes as catkin mentioned, set nullglob and it should solve the problem.

jlinkels · 12-27-2009, 07:49 AM

It works with nullglob enabled. It is the first time I see nullglob being used though. And it was not smart either to disregard the statement in your first example either.

jlinkels