variables in bash scripts - I'm confused

[GrouchyGaijin]

Hi Guys,

I am attempting to learn a bit about writing bash scripts.
The test folder I'm using has 20 files named 1.jpg 2.JPG 3.jpg 4.JPG etc.

I was thinking that I'd like to have a script check if any files with the .JPG extension are in a folder and then tell me yes there are or no there are not.

If I run:

#!/bin/bash
imagejpg=.JPG
if $imagejpg; then
echo "Files Exist" 
fi

I get:

line 6: .JPG: command not found

If I change the script adding ".JPG" (adding the quotes)
I get the same result.

If I change to imagejpg="*.JPG"
I get :

line 6: 10.JPG: command not found

I would really appreciate it if someone could tell me what I am doing wrong.

[schragge]

imagejpg=.JPG
for file in *$imagejpg
do
  if [[ -f $file ]]
  then
    echo Files exist
    break
  fi
done

See Introduction to if, The for loop, and File name expansion

Alternatively, you can do it like this

imagejpg=.JPG
stat -c '' *$imagejpg &>/dev/null && echo Files exist

See stat(1), redirection, and List Constructs

[GrouchyGaijin]

Thank you!
I'll check those links.
You make it look so easy, pretty cool.

[GrouchyGaijin]

I'm back to bug the forum again.

OK

The eventual goal is that when the script is run:
The user will see that the script is looking for a specific type of image file.
The user will be told if that file type exists or not.
If the file type exists the user will be told that all files of that type are being resized.

I have this which is incorrect:

imagejpg=.jpgread -p "Press the [Enter] key to search for jpegs..."
for file in *$imagejpg
do
  if [[ -f $file ]]
  then
    echo We have jpgs
else
echo No jpegs
fi


if [[ -f $file ]]
then
echo "Resizing jpgs"
break
 fi


for file in *$imagejpg


do gm mogrify -resize 720x720 *.jpg


break
done

This is the output in the terminal when I run the script:

Press the [Enter] key to search for jpegs...
/home/john/scripts/test11: line 44: syntax error: unexpected end of file

There is no mention that the directory I'm in has no jpg files.

What am I doing wrong?
I really appreciate the help!!

[schragge]

Why not just

gm mogrify -verbose -resize 720x720 *.jpg

[cortman]

Why not just

gm mogrify -verbose -resize 720x720 *.jpg

Well, this, really. No need for anything else.

I'm back to bug the forum again.

OK

The eventual goal is that when the script is run:
The user will see that the script is looking for a specific type of image file.
The user will be told if that file type exists or not.
If the file type exists the user will be told that all files of that type are being resized.

I have this which is incorrect:

imagejpg=.jpgread -p "Press the [Enter] key to search for jpegs..."
for file in *$imagejpg
do
  if [[ -f $file ]]
  then
    echo We have jpgs
else
echo No jpegs
fi


if [[ -f $file ]]
then
echo "Resizing jpgs"
break
 fi


for file in *$imagejpg


do gm mogrify -resize 720x720 *.jpg


break
done

This is the output in the terminal when I run the script:

Press the [Enter] key to search for jpegs...
/home/john/scripts/test11: line 44: syntax error: unexpected end of file

There is no mention that the directory I'm in has no jpg files.

What am I doing wrong?
I really appreciate the help!!

First, your script is full of syntax errors- read the Bash Beginner's Guide closely- check out each section that deals with a command you use.
As far as how to go about doing this, here's perhaps an improved way (although I'm a scripting beginner myself- someone can feel free to critique this method):

echo "Pres Enter to search for JPEGS"
read start
pics=$(find -maxdepth 1 -regex ".*\.jpe?g" -printf "%f\n")
if [ $pics ] ; then
   echo "Pics found!"
   echo "Resizing..."
   for i in $pics ; do
        gm mogrify -resize 720x720 $i
   done
else
    echo "No pics"
fi

[GrouchyGaijin]

Thank you for the reply. I'll read the guide.
I tried the code you wrote:

echo "Pres Enter to search for JPEGS"
read startpics=$(find -maxdepth 1 -regex ".*\.jpe?g" -printf "%f\n")if [ $pics ] ; then   echo "Pics found!"   echo "Resizing..."   for i in $pics ; do       do gm mogrify -resize 720x720 $i   doneelse    echo "No pics" fi

and got this:

line 10: syntax error near unexpected token 
`do' line 10: `       do gm mogrify -resize 720x720 $i'

[cortman]

The guide is good; I reference it all the time myself.
The problem with the gm mogrify command is that I copy/pasted your line, and I already had a "do" in my for loop, so just delete the "do" and it should work. My mistake!

[GrouchyGaijin]

and it does - how cool is that!
What is the ? in ".*\.jpe?g" for?
How would I change it for images with the extension .JPG or .png?

[steeldriver]

IMO you shouldn't use

if [ $pics ]

or

for i in $pics

Both will break if your search finds any filenames with spaces e.g.

$ ls *.jpg
 978-1-234 5678-9.jpg  978123456789.jpg
$ pics=$(find . -maxdepth 1 -name '*.jpg' -printf "%f\n")
$ if [ $pics ] ; then echo 'Pics found!'; fi
-bash: [: 978-1-234: binary operator expected
$
$ for pic in $pics; do echo $pic; done
978123456789.jpg
978-1-234
5678-9.jpg

A more bullet proof way to do this kind of loop-over-find-results is along the lines of (fill in whatever you want to 'do' instead of echo)

$ while read -rd $'\0' pic; do echo "$pic"; done < <(find . -maxdepth 1 -name '*.jpg' -print0)

You don't really need to test if there are any matches but if you really must then it's better to (a) quote the variable (make it a habit - ALWAYS!) and (b) test to see if the string is non-empty

$ if [ -n "$pics" ] ; then echo 'Pics found!'; fi
Pics found!
$