`tab` is used as a separator In the tab-delimited file. This type of text file is created to store various types of text data in a structured format. Â Different types of command exist in Linux to parse this type of file. Â `awk` command is one of the ways to parse the tab-delimited file in different ways. The uses of the `awk` command to read the tab-delimited file has shown in this tutorial.
Create a tab-delimited file:
Create a text file named users.txt with the following content to test the commands of this tutorial. This file contains the user’s name, email, username, and password.
users.txt
Md. Robin        [email protected]               robin89                563425
Nila Hasan        [email protected]                nila78                245667
Mirza Abbas        [email protected]               mirza23                534788
Aornob Hasan       [email protected]        arnob45                778473
Nuhas Ahsan        [email protected]               nuhas34                563452
Example-1: Print the second column of a tab-delimited file using the -F option
The following `sed` command will print the second column of a tab-delimited text file. Here, the ‘-F’Â option is used to define the field separator of the file.
$ awk -F '\t' '{print $2}' users.txt
The following output will appear after running the commands. The second column of the file contains the user’s email addresses, which are displaying as output.
Example-2: Print the first column of a tab-delimited file using the FS variable
The following `sed` command will print the first column of a tab-delimited text file. Here, FS ( Field Separator) variable is used to define the field separator of the file.
$ awk '{ print $1 }' FS='\t' users.txt
The following output will appear after running the commands. The first column of the file contains the user’s names, which are displaying as output.
Example-3: Print the third column of a tab-delimited file with formatting
The following `sed` command will print the third column of the tab-delimited text file with formatting by using the FS variable and printf. Here, the FS variable is used to define the field separator of the file.
$ awk 'BEGIN{FS="\t"} {printf "%10s\n", $3}' users.txt
The following output will appear after running the commands. The third column of the file contains the username that has been printed here.
Example-4: Print the third and fourth columns of the tab-delimited file by using OFS
OFS (Output Field Separator) is used to add a field separator in the output. The following `awk` command will divide the content of the file based on tab(\t) separator and print the 3rd and 4th columns using the tab(\t) as a separator.
$ awk -F "\t" 'OFS="\t" {print $3, $4 > ("output.txt")}' users.txt
$ cat output.txt
The following output will appear after running the above commands. The 3rd and 4th columns contain the username and password, which have been printed here.
Example-5: Substitute the particular content of the tab-delimited file
sub() function is used in `awk to command for substitution. The following `awk` command will search the number 45 and substitute with the number 90 if the searching number exists in the file. After the substitution, the content of the file will be stored in the output.txt file.
$ awk  -F "\t"'{sub(/45/,90);print}' users.txt > output.txt
$ cat output.txt
The following output will appear after running the above commands. The output.txt file shows the modified content after applying the substitution. Here, the content of the 5th line has modified, and ‘arnob45’ is changed to ‘arnob90’.
Example-6: Add string at the beginning of each line of a tab-delimited file
In the following, the `awk` command, the ‘-F’ option is used to divide the content of the file based on the tab(\t). OFS has used to add a comma(,) as a field separator in the output. sub() function is used to add the string ‘—→’ at the beginning of each line of the output.
$ awk -F "\t" '{{OFS=","};sub(/^/, "---->");print $1,$2,$3}' users.txt
The following output will appear after running the above commands. Each field value is separated by comma(,) and a string is added at the beginning of each line.
Example-7: Substitute the value of a tab-delimited file by using the gsub() function
gsub() function is used in the `awk` command for global substitution. All string values of the file will replace where the searching pattern matches. The main difference between the sub() and gsub() functions is that sub() function stops the substitution task after finding the first match, and the gsub() function searches the pattern at the end of the file for substitution. The following `awk` command will search the word ‘nila’ and ‘Mira’ globally in the file and substitute all occurrences by the text, ‘Invalid Name’, where the searching word matches.
$ awk  -F ‘\t’ '{gsub(/nila|Mira/, "Invalid Name"); print}' users.txt
The following output will appear after running the above commands. The word ‘nila’ exists two times in the 3rd line of the file that has been replaced by the word ‘Invalid Name’ in the output.
Example-8: Print the formatted content from a tab-delimited file
The following `awk` command will print the first and the second columns of the file with formatting by using printf. The output will show the user’s name by enclosing the email address in brackets.
$ awk -F '\t' '{printf "%s(%s)\n", $1,$2}' users.txt
The following output will appear after running the above commands.
Conclusion
Any tab-delimited file can be easily parsed and printed with another delimiter by using the `awk` command. The ways of parsing tab-delimited files and printing in different formats have shown in this tutorial by using multiple examples. The uses of sub() and gsub() functions in the `awk` command for substituting the content of the tab-delimited file are also explained in this tutorial. I hope this tutorial will help the readers to parse the tab-delimited file easily after practicing the examples of this tutorial properly.
