The "Argument list too long" error occurs when you try to pass too many arguments to a shell command. In Unix-like systems, there's a limit to the number of bytes that can be passed to an executable in the argument list (typically around 128KB-2MB depending on the system). When you use wildcards like *.jpg that expand to thousands of files, you easily hit this limit.

Many developers first try using xargs with ls, but this approach fails because:

ls /path/*.jpg | xargs -I {} cp {} /destination/

The problem persists because ls itself hits the argument limit before xargs can process the files.

Method 1: Using find with -exec

The most reliable solution is to use find which doesn't suffer from argument list limitations:

find /home/ftpuser1/public_html/ftparea/ -name "*.jpg" -exec cp -uf {} /home/ftpuser2/public_html/ftparea/ \;

Method 2: find with xargs

For better performance with very large file sets:

find /home/ftpuser1/public_html/ftparea/ -name "*.jpg" -print0 | xargs -0 -I {} cp -uf {} /home/ftpuser2/public_html/ftparea/

The -print0 and -0 options handle filenames with spaces correctly.

Method 3: Using rsync

For recurring copy operations, rsync is more efficient:

rsync -avm --include='*.jpg' -f 'hide,! */' /home/ftpuser1/public_html/ftparea/ /home/ftpuser2/public_html/ftparea/

For directories with millions of files:

• find with -exec is most reliable but slower
• find | xargs offers better performance
• rsync is best for repeated operations

If you need more control over the copy process:

# Using a for loop (slower but more flexible)
for file in /home/ftpuser1/public_html/ftparea/*.jpg; do
    [ -e "$file" ] || continue
    cp -uf "$file" /home/ftpuser2/public_html/ftparea/
done

Remember that the for loop approach will still fail if the wildcard expansion exceeds the argument limit, so it's better suited for smaller file sets.

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When dealing with thousands of files in Linux, you might encounter the frustrating "Argument list too long" error. This happens because the system has a limit on how many arguments can be passed to a command through the shell.

The ARG_MAX limit in Linux (typically around 2MB) defines the maximum length of arguments that can be passed to a new program. When you use wildcards like *.jpg, the shell expands this to all matching filenames before passing to the command.

Method 1: Using find with xargs

find /home/ftpuser1/public_html/ftparea/ -maxdepth 1 -name "*.jpg" -print0 | xargs -0 -I {} cp -uf {} /home/ftpuser2/public_html/ftparea/

Key points:
- -print0 and -0 handle filenames with spaces
- -maxdepth 1 prevents recursion into subdirectories
- Works with tens of thousands of files

Method 2: Using rsync (Best for Large Transfers)

rsync -av --progress /home/ftpuser1/public_html/ftparea/*.jpg /home/ftpuser2/public_html/ftparea/

Advantages:
- Built-in chunking avoids argument limits
- Can resume interrupted transfers
- Shows progress information

Method 3: Using a for Loop

for file in /home/ftpuser1/public_html/ftparea/*.jpg; do
    cp -uf "$file" /home/ftpuser2/public_html/ftparea/
done

Note: Slower but works for moderately large file sets

For the fastest performance with millions of files:

cd /home/ftpuser1/public_html/ftparea/
find . -maxdepth 1 -name "*.jpg" -exec cp -uf {} /home/ftpuser2/public_html/ftparea/ \;

This avoids launching cp for each file individually.

When other methods aren't suitable:

ls /home/ftpuser1/public_html/ftparea/ > /tmp/filelist.txt
while read -r file; do
    cp -uf "$file" /home/ftpuser2/public_html/ftparea/
done < /tmp/filelist.txt