"$@" expands to one shell word per original argument. It is the safe way to forward or loop over all supplied values — spaces inside an argument stay inside it.

Loop over arguments

Print every input path:

for path in "$@"; do
  if [[ -e $path ]]; then
    printf 'exists: %s\n' "$path"
  else
    printf 'missing: %s\n' "$path" >&2
  fi
done

Test paths containing spaces, dashes, and wildcard characters. Each must remain one value:

./check-paths 'weekly report.txt' notes.md
# exists: weekly report.txt
# missing: notes.md

The quotes carry the whole guarantee. Unquoted $@ or $* splits weekly report.txt into two words, and the loop checks two files that don’t exist. Same inside the loop body: "$path" keeps the value whole.

Loop over files with globs

For files on disk, let the shell expand a glob:

for logfile in /var/log/nginx/*.log; do
  printf 'compressing %s\n' "$logfile"
done

The expansion happens before the loop starts, and each match arrives as one word. Filenames with spaces are safe with no extra effort.

One trap remains: a glob that may match nothing. When no file matches, Bash leaves the pattern in place, and your loop runs once with the literal string /var/log/nginx/*.log as its value. The script then claims to compress a file that doesn’t exist. Fix it with nullglob:

shopt -s nullglob
for logfile in /var/log/nginx/*.log; do
  printf 'compressing %s\n' "$logfile"
done

With nullglob set, an unmatched glob expands to nothing and the loop body never runs. Test both states: a directory with matching files and an empty one.

Do not parse ls

Old tutorials show for f in $(ls). Don’t copy it. The output of ls is text, and command substitution word-splits it, so any filename with a space shatters into pieces. There is no quoting fix for this pattern — the information is already destroyed.

Work from arguments, globs, find -print0, or another structured source. The find variant gets its own lesson in the next module.

Loop over arguments and files