sed Delete / Remove ^M Carriage Return (Line Feed / CRLF) on Linux or Unix

How can I remove the ^M or ^M (carriage Return / line feed ) from text file using sed under UNIX or Linux operating systems?

A newline is nothing but end of line (EOL). It is a special character or sequence of characters signifying the end of a line of text and the start of a new line. The actual codes representing a newline vary across operating systems. For example CR+LF is used by Microsoft Windows, DOS (MS-DOS, PC DOS, etc.). LF is used by Unix and Unix-like systems including Linux, OS X, FreeBSD and more. The procedure is as follows:

1. Type the following sed command to delete a carriage Return (CR)
2. sed 's/\r//' input > output
3. Type the following sed command to replace a linefeed(LF)
4. sed ':a;N;$!ba;s/\n//g' input > output

Delete a carriage return (CR) with sed command

The substitute command syntax is as follows (to get ^M type CTRL+V followed by CTRL+M i.e. don’t just type the carat symbol and a capital M. It will not work):

sed -e 's/^M//g' input
sed -e 's/^M//g' input > output
# gnu sed syntax
sed -i 's/^M//g' input
# replace it with FOO
sed -i -e 's/^M/FOO/g' input

OR easy to use sed syntax to remove carriage return in Unix or Linux:

sed 's/\r$//' input > output
sed 's/\r$//g' input > output 
# GNU/sed syntax
sed -i 's/\r$//g' input

To replace a carriage return (CR) with sed command

The syntax is:
sed 's/\r/YOUR-replacement-TEXT-HERE/' input > output
sed 's/\r/YOUR-replacement-TEXT-HERE/g' input > output
sed 's/\r/foo/g' input > output

How to verify ^M in a text file

Use the cat command as follows:
cat -v input
Sample outputs:

A note about deleting or replacing a linefeed (LF) with sed on Unix or Linux

Use the following syntax if you do not want to delete \n (new line):
sed -i ':a;N;$!ba;s/\n//g' input
OR
sed ':a;N;$!ba;s/\n//g' input > output
See sed command man page for more info.

Remove a carriage return with dos2unix command

You can also use dos2unix command to converts text files from the DOS format to the Unix format:

dos2unix input
dos2unix -b input

The tr command syntax

To delete a CRLF:
tr -d '\r' < input > output