From Linux Shell Scripting Tutorial - A Beginner's handbook
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  • The IFS is a special shell variable.
  • You can change the value of IFS as per your requirments.
  • The Internal Field Separator (IFS) that is used for word splitting after expansion and to split lines into words with the read builtin command.
  • The default value is <space><tab><newline>. You can print it with the following command:
cat -etv <<<"$IFS"
  • IFS variable is commonly used with read command, parameter expansions and command substitution.

From the bash man page:

The shell treats each character of IFS as a delimiter, and splits the results of the other expansions into words on these characters. If IFS is unset, or its value is exactly <space><tab><newline>, the default, then sequences of <space>, <tab>, and <newline> at the beginning and end of the results of the previous expansions are ignored, and any sequence of IFS characters not at the beginning or end serves to delimit words. If IFS has a value other than the default, then sequences of the whitespace characters space and tab are ignored at the beginning and end of the word, as long as the whitespace character is in the value of IFS (an IFS whitespace character). Any character in IFS that is not IFS whitespace, along with any adjacent IFS whitespace characters, delimits a field. A sequence of IFS whitespace characters is also treated as a delimiter. If the value of IFS is null, no word splitting occurs.

  • The default value of IFS is a space, a tab, and a newline.


Create a text file called /tmp/domains.txt as follows:


Create a shell script called setupapachevhost.sh as follows:

# setupapachevhost.sh - Apache webhosting automation demo script

# set the Internal Field Separator to |
while read domain ip webroot ftpusername
        printf "*** Adding %s to httpd.conf...\n" $domain
        printf "Setting virtual host using %s ip...\n" $ip
        printf "DocumentRoot is set to %s\n" $webroot
        printf "Adding ftp access for %s using %s ftp account...\n\n" $domain $ftpusername
done < "$file"

Save and close the file. Run it as follows:

chmod +x setupapachevhost.sh

Sample outputs:

*** Adding cyberciti.biz to httpd.conf...
Setting virtual host using ip...
DocumentRoot is set to /home/httpd
Adding ftp access for cyberciti.biz using ftpcbzuser ftp account...

*** Adding nixcraft.com to httpd.conf...
Setting virtual host using ip...
DocumentRoot is set to /home/httpd
Adding ftp access for nixcraft.com using ftpnixuser ftp account...