simple shell script to iterate the files

varunbihani · 02-19-2007, 08:31 PM

I want to write a shell script that will read the files in the directory and then i would need to each file (name) as the parameter to command (to run java class)

For(each file in the directory)
{
java testjava.java file_name
}

fukawi2 · 02-19-2007, 08:50 PM

Code:

for fname in $(ls) ; do

Doesn't work for files with spaces in the name though

varunbihani · 02-19-2007, 08:57 PM

Is it possible to do the ls to get only files with ".java" extension ?
Also, I would like to read the subdirectories ?

fukawi2 · 02-19-2007, 09:05 PM

Code:

for fname in $(ls *.java) ; do

Not sure about the sub-directories... Try the -R flag for ls which is recursive. I'm not sure if it will output it in the correct format for bash to interpret.

tbutttbutt · 02-19-2007, 09:07 PM

You need a loop like:

for i in `ls`
do
case $i in
.) ;;
,,) ;;
*) java testjava.java $i;;
esac
done

colucix · 02-20-2007, 01:49 AM

Quote:

Originally Posted by varunbihani

Also, I would like to read the subdirectories ?

The find command is more suitable for looking into subdirectories:

Code:

find . -type f -name "*.java" -exec your_command_here {} \;

where the option -exec execute your commands on each file found. It should take care of blank spaces inside filename, too. See man find for details.

fukawi2 · 02-20-2007, 04:01 PM

Thanks colucix - I didn't think of that

timmeke · 02-21-2007, 05:27 AM

To make "ls" work with spaces in filenames, just play around with the IFS variable.
By default, $IFS contains a space, a tab and a newline character, so output of ls is split on all those, including the spaces in the names of files.
Setting $IFS to only include the newline will avoid this.
You can restore $IFS to it's normal setting afterwards too.

Code:

backup=${IFS}
IFS="\n"
for i `ls`; do
...
done
IFS=${backup}

or something like that...

But in this case, the "find" command is indeed a better solution.

fukawi2 · 02-21-2007, 05:55 AM

I never knew that variable existed timmeke - cheers

BUT... :P
Setting it to only a new line would mean you'd have to alter the output of ls with the -l option wouldn't it? and then you would get all the other output (permissions, dates, size etc) that goes with the -l option...

Nick_Battle · 02-21-2007, 06:25 AM

Quote:

Originally Posted by fukawi2

Setting it to only a new line would mean you'd have to alter the output of ls with the -l option wouldn't it?

The default ls command only produces output that goes across the line when it knows it's writing to a tty device (a terminal of some sort). When it's being used in scripts, with its output being used as here, it outputs in a column.

Try typing "ls | cat" on a terminal :-)

fukawi2 · 02-21-2007, 03:35 PM

Well butter my butt and call me a biscuit... Cool!

timmeke · 02-22-2007, 01:23 AM

Or you can use the "-1" (that's number one, not the letter l) option of ls to force printing in one column.