Line endings: LF and CRLF

In short: Windows ends lines with two characters (CR+LF), Linux and macOS with one (LF). The difference keeps causing trouble in scripts and Git.

In more detail: CR (“carriage return”) and LF (“line feed”) come from typewriters and teleprinters. Windows kept both, Unix only LF.

In Depth

• Symptoms: A shell script with CRLF aborts with bad interpreter: /bin/bash^M. Files look single-lined in old editors or show ^M.
• Git: core.autocrlf converts on checkin and checkout. More reliable is a .gitattributes file with * text=auto and *.sh text eol=lf.
• Converting: dos2unix and unix2dos, the “line ending” setting in editors.
• Protocols: HTTP, SMTP and many text protocols require CRLF, even on Linux.
• Old Macs: Formerly only CR, no longer common.
• Note: In Python text mode, line endings are normalised on reading (\n).

See also: git rebase