Basic Bash Loop Fails Help.

[Gen2ly]

I admit this is my first loop. From what I've read this is the right way to create a loop but the loop only runs once and quits. I believe this has something to do with the variable-reference.

What I'm looking to do is create a script that I can type


command *.png

and all pngs will be run through the script. Here's the script:


#!/bin/bash
# resize-image-new - makes new image and resizes.
# http://www.imagemagick.org/www/command-line-options.html

# Fixes / ToDo
# add ability to subtract enhance flag
# add looping: resize-new-image 400 *.png

SIZE=$1
NAME=$2
COLORS=2048
DEPTH=16
RESIZEDNAME="${NAME%.*}"-"$SIZE".png
#ENHANCE - options to enhance image -enhance smoothes rough images

if [[ -z $NAME ]]; then
echo "resize-image <WIDTHxHEIGHT> <original-image>"
exit;
fi

# Convert (SIZE is proportional least value is used and only x needs specifid.)
# Compress PNG

for i in "$NAME"; do
convert -resize "$SIZE" -enhance "$NAME" "$RESIZEDNAME"
mogrify -colors $COLORS -depth $DEPTH "$RESIZEDNAME"
optipng -o5 "$RESIZEDNAME"
done

The script works fine by typing:


command picture.png

However specifying *.png will only loop once. What am I notunderstandigng here?

[Quikee]

If you have pictures 1.png, 2.png and 3.png, specifying "command *.png" will execute "command 1.png 2.png 3.png".

What you will need to do is loop through input arguments the following (or any other) way:


for i in "$*"; do
echo $i
done

[Gen2ly]

hmm, this is going to required a more involved process. I actually have set another variable before the filename


resize-image-new size filename.png

so using "$*" isn't going to work as it will grab "size filename.png" hmm, any idea? My initial thought is to use "$*" and then bash filter out size. Would that do it?

[Quikee]

hmm, this is going to required a more involved process. I actually have set another variable before the filename


resize-image-new size filename.png

so using "$*" isn't going to work as it will grab "size filename.png" hmm, any idea? My initial thought is to use "$*" and then bash filter out size. Would that do it?

I am not a bash expert but I would do something like this then:


count = 0
for i in "$*"; do
if [ $count != 0 ]; then
do except for first argument
fi
let count = count + 1
done

[mssever]

After getting the first value (size or whatever), use the shift command to knock it off the list of positional parameters. Then,
for i in "$@"; do
#do something with "$i", making sure to always put it in double quotes
doneNote "$@" instead of "$*". $* in quotes expands all positional parameters to a single string, while $@ in quotes keeps the parameters separate.

[Gen2ly]

hmm, I'm going to have to learn more about bash. I'm reading what looks like to be a pretty good guide (http://wooledge.org:8000/BashGuide). Thanks for pointing me in the right direction. I'll see what I can figure out.

[zippaplick]

Look at the shift command for bash for a simple way to pick off the cmd line args.
This snippet will pick off the first arg then loop through the rest.




#!/bin/sh
echo "SIZE: $1"
echo "THE PNGs:"
shift
while [ $# -gt 0 ] ; do
# do something interesting with each png
echo $1
shift
done