Comments on: Bash Shell Loop Over Set of Files

By: Vivek Gite

Vivek Gite — Wed, 11 Jan 2012 08:27:20 +0000

Pure bash code and nothing else :)

filecount=(*.pdf)
echo "Total files in $PWD: ${#filecount[@]}"

By: Potato

Potato — Wed, 11 Jan 2012 00:26:53 +0000

try COUNT=`ls -1 *.pdf | wc -l`

By: RDuke

RDuke — Tue, 10 Jan 2012 15:32:56 +0000

@saad: maybe something like

count=$( ls -1 *.pdf | wc -l )

By: Saad

Saad — Tue, 10 Jan 2012 06:48:39 +0000

Is it possible to know how many files will this loop run on,

e.g. in the following loop

for f in *.pdf
do

done;

can i know how many files are present in *.pdf glob, and can i use that to know how many files have been processed out of the total number

By: Hari

Hari — Wed, 07 Dec 2011 12:21:58 +0000

Hello I have a problem .i want to run a program N times by give N number of different .txt files from a directory. i want to give all the files in single time by using loops can any one help me to script .

By: monr4

monr4 — Fri, 15 Jul 2011 21:09:39 +0000

hello, a have a problem, i need to do a script por a rutine something like

for i in $(cat list1) but with 2 list
for i in $(cat list1) AND b in $(cat list2);do mknod /dev/$i/group c64[$b];done

somebody helpme with that please

By: Vivek Gite

Vivek Gite — Sat, 25 Jun 2011 15:29:34 +0000

Also, see HowTo: Use Bash Parameter Substitution Like A Pro

By: TheBonsai

TheBonsai — Sat, 25 Jun 2011 14:46:24 +0000

http://wiki.bash-hackers.org/syntax/pe#common_use

By: Benjamin

Benjamin — Fri, 24 Jun 2011 20:12:48 +0000

Nice compilation, thanks! One suggestion, though: I think many people would be looking for still another thing: how to get file extensions and how to get filenames without extensions.

By: she

she — Mon, 07 Mar 2011 16:21:56 +0000

can somebody help me develop a program that has the option whether to overwrite a document or not. when making a file, it will ask the user if he would want to create a new file on the same file name or overwrite the said filename.. please i need this badly.

By: Xa

Xa — Sun, 19 Dec 2010 04:14:30 +0000

for i in ‘ls’
did NOT work for me. What does work is this:
for i in $(ls)

By: Vivek Gite

Vivek Gite — Thu, 17 Dec 2009 06:29:17 +0000

@gurpur

Again, offtopic, go to our forum at nixcraft.com to post all your shell scripting related queries.

By: gurpur

gurpur — Thu, 17 Dec 2009 03:29:35 +0000

I need some in writing a script that will delete a specific line from a bunch of file in a directory.
your help is appreciated

By: TheBonsai

TheBonsai — Tue, 05 May 2009 04:57:18 +0000

@Jeff Schroeder:

The for is easier to read, but it is really annoying when your scripts fail with the dreaded “argument list too long” errors.

This won’t happen on a for-loop statement, since no exec() is done for the loop itself.

By: rduke15

rduke15 — Sun, 12 Apr 2009 14:53:57 +0000

Found the problem with my previous example. The nullglob shell option needs to be set: shopt -s nullglob; for file in *.jpg; do echo " the file variable is now '$file' " ; done produces no output, as expected. As opposed to:

shopt -u nullglob; for file in *.jpg; do echo " the file variable is now '$file' " ; done
the file variable is now '*.jpg'

By: rduke15

rduke15 — Sun, 12 Apr 2009 14:40:47 +0000

One curious problem. If there are NO files matching the glob, you get this:
$ for file in *.jpg; do echo " the file variable is now '$file' " ; done
the file variable is now ‘*.jpg’

I would have expected that the contents of the for loop would not be executed at all, since there was no jpg file.

By: Michael Smith

Michael Smith — Wed, 11 Feb 2009 22:00:25 +0000

I was initially a little confused by the thread. It's not useful to assign * to a variable if you only intend to use it for a loop. Furthermore, as others have stated, putting quotes around the variable name prevent the glob, in this case *, from expanding. * Vivek is not correct that $FILES should be quoted. * DAY's initial response that $FILES should be unquoted is not wrong, but using the variable at all is not useful. * DAY's second idea of looping over the output of `ls` is a very common mistake. It's wrong because of wordsplitting. * Brock Noland's instinct to use for file in *.c... is spot-on. * Jeff Schroeder is right to avoid ARG_MAX in general, but it only applies when you call exec*() via the kernel. Since for is a shell builtin, ARG_MAX doesn't apply here. * David Thompson and Baz's comments are OK, but to Baz I would reiterate to avoid using the ls command for anything except human-readable output. * As for Chris' comment: FILES="*" and FILES=* are equivalent since sh-compliant shells don't expand globs during variable assignment.

By: Foo

Foo — Wed, 11 Feb 2009 21:47:15 +0000

FILES=*; for f in $FILES; do… is WRONG.
for f in `ls`; do… is even WORSE.
Both break with filenames including whitespaces, newlines etc.

Since this is about bash use array if you want files in variables:
files=(*.c)
for f in “${files[@]}”; do cmd “$f”; done

Or just use glob:
for f in *.c; do cmd “$f”; done

By: Chris

Chris — Thu, 11 Dec 2008 01:00:45 +0000

> FILES=”*” is wrong unless you want the value of $FILES to be *. The same is true of “*.c”. Lose the quotes to get what you want.

I dont think his wrong. He just gave those of us who are new to Bash scripting a placeholder for other commands or values. In fairness, the script did what it said it would do. Thanks for explaining the difference with using quotes and doing away with them.

For others reading this. Dont just take our words for it. Use the script – test it for yourself. Play with it. Thanks and congratulations to nixcraft for sharing.

Peace!

By: Baz

Baz — Sun, 08 Jun 2008 00:12:52 +0000

Double quotes disable the special meaning of most enclosed characters. They do not disable the interpretation of variables with a leading $. To do this yopu need single quotes.

FILES=”*” is wrong unless you want the value of $FILES to be *. The same is true of “*.c”. Lose the quotes to get what you want.

I have always just used -

for F in *
do
… etc

for F in `ls`
is OK except that
for F in ls -1 (one)
is better, but both are more cumbersome and less elegant that
for F in * (or *.c and so on)