Combination of cat and grep Commands to Filter Output

Combination of cat and grep Commands to Filter Output
Combination of cat and grep Commands to Filter Output

Combination of cat and grep Commands to Filter Output - Navigating the intricacies of the Linux command line is a journey that unveils a plethora of powerful tools, and among the indispensable ones are the 'cat' and 'grep' commands. 

In the realm of Linux systems, these commands stand as stalwarts, offering users unparalleled capabilities in handling and extracting information from text files. The 'cat' command, short for concatenate, serves as a versatile file manipulation tool, while 'grep,' derived from the phrase Global Regular Expression Print, excels in pattern matching within files.

Together, they form a dynamic duo that empowers users to efficiently sift through and manipulate textual data, making them essential components of any Linux user's toolkit. 

In this exploration, we delve into the functionality and synergy of the 'cat' and 'grep' commands, uncovering the nuanced ways in which they contribute to a streamlined and powerful command-line experience in the Linux environment.


I have a log, where log records all application activity on the server, and the log is confirmed by the request time, at one time there was a case where I was required to retrieve the log and must select only logs on "25 October 2020" with a request time of "more than 6 seconds".

Ex. Log: - - [25/Oct/2020:12:00:00 +0700] TLSv1.2/ECDHE-RSA-AES256-SHA384 "POST /kitsake/blogspot/com HTTP/1.1" 200 765 0.336 "-" "-" "-" "0.336"
ex output of log format
ex output of log format

Wich one: : Sender's IP
[25/Oct/2020:12:00:00 +0700] : date:time:gmt
TLSv1.2/ECDHE-RSA-AES256-SHA384 : TLS Information from the Sender
"POST /kitsake/blogspot/com HTTP/1.1" 200 : Sent with a Status of 200 
0.336 "-" "-" "-" "0.336" : Request Time Information with Second Calculation


From the log, we can get the format information of the output that is displayed, and now we create a command which combines "cat: to browse the file" and "grep: to filter what you want to display"


# cat [filenameoflog] |grep [date/time/gmt] |grep [requesttime]

In this case, I took the request time format that was "", keep in mind that the character must also be entered because it is susceptible. so from the start we will take logs that are longer than 6 seconds:

"[6-9] =" 6,7,8,9 seconds
. [0-9] = "1,2,3,4,5,6,7,8,9 milliseconds
[0-9] = "1,2,3,4,5,6,7,8,9 milliseconds
[0-9] "=" 1,2,3,4,5,6,7,8,9 milliseconds


ok let's try with the command below

# cat | grep '25/Oct/2020' | grep '"[6-9].[0-9][0-9][0-9]"' | grep '"[1-9][1-9].[0-9][0-9][0-9]"'
ex output of log with filtering
ex output of log with filtering

Closing statement

In conclusion, the combination of the 'cat' and 'grep' commands presents a formidable solution for efficiently navigating and filtering through textual data within the Linux environment. 

By harnessing the power of these commands, users can seamlessly extract and manipulate information from log files, as demonstrated in the exploration above. This dynamic duo proves invaluable, particularly when faced with tasks such as isolating specific logs based on date and request time criteria. 

As we continue to explore the vast capabilities of the Linux command line, the synergy between 'cat' and 'grep' stands as a testament to the flexibility and power of open-source tools. With this knowledge in hand, users can confidently tackle various data manipulation challenges, enhancing their command-line experience.

Maybe that's all I can share with you guys, hopefully this article will be useful.

Thank You.

Bangkit Ade Saputra
Bangkit Ade Saputra At the end of the day, my job involves people. we're complicated, we're always changing, we have millions of things going on in our lives, and changing jobs is always a big decision.

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