How to find out line-endings in a text file?

Question

I\'m trying to use something in bash to show me the line endings in a file printed rather than interpreted. The file is a dump from SSIS/SQL Server being read in by a Linux

Answer 1

Try file then file -k then dos2unix -ih

file will usually be enough. But for tough cases try file -k or dosunix -ih.

Details below.

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Try file -k

Short version: file -k somefile.txt will tell you.

• It will output with CRLF line endings for DOS/Windows line endings.
• It will output with LF line endings for MAC line endings.
• And for Linux/Unix line "CR" it will just output text. (So if it does not explicitly mention any kind of line endings then this implicitly means: "CR line endings".)

Long version see below.

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Real world example: Certificate Encoding

I sometimes have to check this for PEM certificate files.

The trouble with regular file is this: Sometimes it's trying to be too smart/too specific.

Let's try a little quiz: I've got some files. And one of these files has different line endings. Which one?

(By the way: this is what one of my typical "certificate work" directories looks like.)

Let's try regular file:

$ file -- *
0.example.end.cer:         PEM certificate
0.example.end.key:         PEM RSA private key
1.example.int.cer:         PEM certificate
2.example.root.cer:        PEM certificate
example.opensslconfig.ini: ASCII text
example.req:               PEM certificate request

Huh. It's not telling me the line endings. And I already knew that those were cert files. I didn't need "file" to tell me that.

What else can you try?

You might try dos2unix with the --info switch like this:

$ dos2unix --info -- *
  37       0       0  no_bom    text    0.example.end.cer
   0      27       0  no_bom    text    0.example.end.key
   0      28       0  no_bom    text    1.example.int.cer
   0      25       0  no_bom    text    2.example.root.cer
   0      35       0  no_bom    text    example.opensslconfig.ini
   0      19       0  no_bom    text    example.req

So that tells you that: yup, "0.example.end.cer" must be the odd man out. But what kind of line endings are there? Do you know the dos2unix output format by heart? (I don't.)

But fortunately there's the --keep-going (or -k for short) option in file:

$ file --keep-going -- *
0.example.end.cer:         PEM certificate\012- , ASCII text, with CRLF line terminators\012- data
0.example.end.key:         PEM RSA private key\012- , ASCII text\012- data
1.example.int.cer:         PEM certificate\012- , ASCII text\012- data
2.example.root.cer:        PEM certificate\012- , ASCII text\012- data
example.opensslconfig.ini: ASCII text\012- data
example.req:               PEM certificate request\012- , ASCII text\012- data

Excellent! Now we know that our odd file has DOS (CRLF) line endings. (And the other files have Unix (LF) line endings. This is not explicit in this output. It's implicit. It's just the way file expects a "regular" text file to be.)

(If you wanna share my mnemonic: "L" is for "Linux" and for "LF".)

Now let's convert the culprit and try again:

$ dos2unix -- 0.example.end.cer

$ file --keep-going -- *
0.example.end.cer:         PEM certificate\012- , ASCII text\012- data
0.example.end.key:         PEM RSA private key\012- , ASCII text\012- data
1.example.int.cer:         PEM certificate\012- , ASCII text\012- data
2.example.root.cer:        PEM certificate\012- , ASCII text\012- data
example.opensslconfig.ini: ASCII text\012- data
example.req:               PEM certificate request\012- , ASCII text\012- data  

Good. Now all certs have Unix line endings.

Try dos2unix -ih

I didn't know this when I was writing the example above but:

Actually it turns out that dos2unix will give you a header line if you use -ih (short for --info=h) like so:

$ dos2unix -ih -- *
 DOS    UNIX     MAC  BOM       TXTBIN  FILE
   0      37       0  no_bom    text    0.example.end.cer
   0      27       0  no_bom    text    0.example.end.key
   0      28       0  no_bom    text    1.example.int.cer
   0      25       0  no_bom    text    2.example.root.cer
   0      35       0  no_bom    text    example.opensslconfig.ini
   0      19       0  no_bom    text    example.req

And another "actually" moment: The header format is really easy to remember: Here's two mnemonics:

1. It's DUMB (left to right: d for Dos, u for Unix, m for Mac, b for BOM).
2. And also: "DUM" is just the alphabetical ordering of D, U and M.

Further reading

• man file
• man dos2unix
• Wikipedia: Newline