Circumvent Argument list too long in script (for loop) - linux

Question

I've seen a few answers regarding this, but as a newbie, I don't really understand how to implement that in my script.
it should be pretty easy (for those who can stuff like this)
I'm using a simple
for f in "/drive1/"images*.{jpg,png}; do
but this is simply overloading and giving me
Argument list too long
How is this easiest solved?

Answer 1

Argument list too long workaroud
Argument list length is something limited by your config.
getconf ARG_MAX
2097152
But after discuss around differences between bash specifics and system (os) limitations (see comments from that other guy), this question seem wrong:
Regarding discuss on comments, OP tried something like:
ls "/simple path"/image*.{jpg,png} | wc -l
bash: /bin/ls: Argument list too long
This happen because of OS limitation, not bash!!
But tested with OP code, this work finely
for file in ./"simple path"/image*.{jpg,png} ;do echo -n a;done | wc -c
70980
Like:
printf "%c" ./"simple path"/image*.{jpg,png} | wc -c
Reduce line length by reducing fixed part:
First step: you could reduce argument length by:
cd "/drive1/"
ls images*.{jpg,png} | wc -l
But when number of file will grow, you'll be buggy again...
More general workaround:
find "/drive1/" -type f \( -name '*.jpg' -o -name '*.png' \) -exec myscript {} +
If you want this to NOT be recursive, you may add -maxdepth as 1st option:
find "/drive1/" -maxdepth 1 -type f \( -name '*.jpg' -o -name '*.png' \) \
-exec myscript {} +
There, myscript will by run with filenames as arguments. The command line for myscript is built up until it reaches a system-defined limit.
myscript /drive1/file1.jpg '/drive1/File Name2.png' /drive1/...
From man find:
-exec command {} +
This variant of the -exec action runs the specified command on
the selected files, but the command line is built by appending
each selected file name at the end; the total number of invoca‐
tions of the command will be much less than the number of
matched files. The command line is built in much the same way
that xargs builds its command lines. Only one instance of `{}'
Inscript sample
You could create your script like
#!/bin/bash
target=( "/drive1" "/Drive 2/Pictures" )
[ "$1" = "--run" ] && exec find "${target[#]}" -type f \( -name '*.jpg' -o \
-name '*.png' \) -exec $0 {} +
for file ;do
echo Process "$file"
done
Then you have to run this with --run as argument.
work with any number of files! (Recursively! See maxdepth option)
permit many target
permit spaces and special characters in file and directrories names
you could run same script directly on files, without --run:
./myscript hello world 'hello world'
Process hello
Process world
Process hello world
Using pure bash
Using arrays, you could do things like:
allfiles=( "/drive 1"/images*.{jpg,png} )
[ -f "$allfiles" ] || { echo No file found.; exit ;}
echo Number of files: ${#allfiles[#]}
for file in "${allfiles[#]}";do
echo Process "$file"
done

Answer 2

There's also a while read loop:
find "/drive1/" -maxdepth 1 -mindepth 1 -type f \( -name '*.jpg' -o -name '*.png' \) |
while IFS= read -r file; do
or with zero terminated files:
find "/drive1/" -maxdepth 1 -mindepth 1 -type f \( -name '*.jpg' -o -name '*.png' \) -print0 |
while IFS= read -r -d '' file; do