tr Command Reference for CI Scripts

tr maps or removes individual characters as text streams through it.

tr is the simplest character-level transformer: uppercase a string, strip carriage returns, squeeze whitespace. It only reads stdin and does not take a filename.

Common flags/usage

• -d: delete characters in set1
• -s: squeeze repeats of set1 into one
• -c / -C: complement set1 (everything not in it)
• [:class:]: character classes like [:alnum:], [:space:]
• a-z: character ranges

Example

BRANCH=$(echo "${GITHUB_REF_NAME}" | tr '/' '-')   # slug for a tag
tr -d '\r' < dos.txt > unix.txt                     # strip CRLF
echo "${RAW}" | tr -cd '[:alnum:]-'

In CI

tr only reads stdin, so tr ... file.txt treats file.txt as a second set, not a file; redirect with < file or pipe in. A reverse-collating-order error on a range like a-Z comes from a locale-confused range; use LC_ALL=C or explicit [:upper:]/[:lower:] classes. Stripping \r fixes CRLF parsing bugs.

Key takeaways

• tr reads only stdin; redirect a file in with < instead of naming it.
• tr -d "\r" converts CRLF files so downstream parsing does not choke.
• Use [:upper:]/[:lower:] classes or LC_ALL=C to avoid locale range errors.

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