Why Do Windows and Linux Scripts Fail? Master Line Ending Differences

Format Differences

End‑of‑line (EOL) characters mark the end of a text line; the actual code varies by OS.

Windows/DOS uses CR+LF (\r\n), Unix/Linux and macOS use LF (\n), classic Mac OS uses CR (\r).

CR is ASCII 0x0D (\r), LF is ASCII 0x0A (\n); DOS shows CR as ^M when viewed on Unix.

Example script test-dos.sh:

#!/bin/bash
echo "Hello World !"

Impact of Format

Visual Impact

Opening a Unix/Mac file in Windows may display all text on a single line.

Opening a Windows file in Unix/Mac often shows an extra ^M at line ends.

Functional Impact

Shell or Python scripts created on Windows may fail on Linux with bad interpreter: No such file or directory errors caused by ^M.

During make, a missing mksh may be reported because of the wrong line ending.

-bash: ./test.sh: /bin/bash^M: bad interpreter: No such file or directory
make[3]: ./mksh: Command not found

Viewing Format

Windows

Editors such as VS Code, UltraEdit, Notepad2 show CR+LF for Windows format or LF for Linux format.

Notepad++ can search for \r\n to identify DOS format.

Linux

cat -v

displays ^M at the end of each line. cat -T shows tabs as ^I. od -c and hexdump -c reveal the raw byte sequence.

Vim status bar indicates file format, e.g., "test-dos.sh" [noeol][dos] 2L, 33B.

cat -v test-dos.sh
#!/bin/bash^M
echo "Hello World !"^M

od -c test-dos.sh
0000000   # ! / b i n / b a s h \r 
 e c h
0000020   o   "   H e l l o   W o r l d   !

Modifying Format

Windows

In VS Code, click the CRLF indicator in the status bar and switch to LF.

Notepad2 offers a “Line Endings” menu to change the format.

Notepad++ can replace \r\n with \n using Find & Replace.

Linux

Special Tools

In Vim, execute :set ff=unix or :set fileformat=unix to convert to Unix format. dos2unix converts DOS files to Unix; unix2dos does the opposite. fromdos (part of tofrodos) converts DOS to Unix.

dos2unix test-dos.sh
# converts in‑place

dos2unix -n test-dos.sh test-unix.sh
# creates a new Unix‑formatted file

Text‑Processing Tools

sed 's/^M//' test-dos.sh > test-unix.sh

removes CR characters from a single file.

Convert many files: find ./ -type f -print0 | xargs -0 sed -i 's/^M$//' In Vim: :%s/^M//g (enter Ctrl+V M for ^M) then :wq. tr -d "\015" test-dos.sh > test-unix.sh deletes CR characters.

Perl one‑liners: cat test-dos.sh | perl -pe 's/\r//g' > test-unix.sh or perl -p -e 's/\r\n/\n/g' test-dos.sh.

sed 's/^M//' test-dos.sh > test-unix.sh
find ./ -type f -print0 | xargs -0 sed -i 's/^M$//'
tr -d "\015" test-dos.sh > test-unix.sh
perl -pe 's/\r//g' test-dos.sh > test-unix.sh