Consider the below command: The above command will display only the repeated lines. [ Free download: Advanced Linux commands cheat sheet.] Please keep in mind that the uniq command prints only the first duplicate line and discards other duplicate lines. You can direct our output to a separate file instead of the normal stdout (terminal). I used a real system log but edited it for demonstration purposes. Note that this file is not sorted, and the duplicate lines are not adjacent to each other. The syntax of this is quite easy to understand.
3. If you run uniq with no options, it behaves as though you used the -u (unique lines) option.
By default, uniq is case-sensitive. It discards all the identical lines and writes the output. Suppose the file contains following lines: Clearly, …
When we sort the file, it groups the duplicate lines, and uniq treats them as duplicates. Consider the below command: The above command will ignore the first two characters in comparison from the file 'dupli.txt'. How to remove duplicate lines on Linux with uniq command. It discards non-duplicate lines. For this, -w command line option is used. Some involve only uniq, and others rely on additional commands.
Let's see how the uniq command works and how it supplements the sort command. This helps us understand the behavior of the uniq command: Below, in the next example, we’re using the -c option to count the repeated lines.
The Linux uniq command whips through your text files looking for unique or duplicate lines. Here, you get the inverse output of the previous command. How-To Geek is where you turn when you want experts to explain technology. The content in the file must be therefore sorted before using uniq or you can simply use sort -u instead f uniq. Therefore, line ChhatrapatiShahuMaharaj has been discarded in the below example: In the below example, I’ve used the -c option to cross-check whether the -d option is only printing the repeated lines or not: The -D option prints repeated lines and discards the non-duplicate lines. Explore the tail and head commands as new additions to your sysadmin toolbox for manipulating and reading text. It can be used by itself but it is commonly used in along with other commands like to identify redundant information in a file. Also, it can be used to display a count of any word, only repeated lines, ignore characters, and compare specific fields. For example, check out the output from the following command: The lines “I Believe I’ll dust my broom” and “I believe I’ll dust my broom” aren’t treated as duplicates because of the difference in case on the “B” in “believe.”. 5. Now, we have a presorted file to work with. Therefore, in the below example, it prints ChhatrapatiShahuMaharaj as an output: Using the -i option, we can ignore the case sensitivity of characters. If INPUT is not specified, uniq reads from the standard input. Dave is a Linux evangelist and open source advocate. The uniq command is fast, flexible, and great at what it does.
You can also skip fields (a run of characters and some white space) instead of characters. uniq does not detect repeated lines unless they are adjacent. Now, let’s understand the use of this with the help of an example. First, let me run through some examples to familiarize you with ‘uniq’ before mixing in other commands and potentially confusing things. If you practice, though, you’ll be well on your way. After reviewing the multiple uniq command options, I would like to share a small image to keep it with you for reference. Now, lets’s use uniq command to remove them: As you can see that we just used the name of input file in the above uniq example and as we didn’t use any output file to store the produced output, the uniq command displayed the filtered output on the standard output with all the duplicate lines removed.
Here is the example: Just like skipping characters, we can consider characters as well using the -w option, such as in the example: Use the --version option to check the version of the uniq command. The uniq command in Linux is a command line utility that reports or filters out the repeated lines in a file. However, if you want, you want to have a NULL terminated output instead (useful while dealing with uniq in scripts). This is the default. Most of the file has already been sorted into adjacent order, but I’ve left a couple lines “out of place” to show the functionality of uniq command. -D: It is used to print all the duplicate lines. In the following example, we’re skipping the first field (first column) to compare the duplicate lines from the second field. We’ll type the following to pipe the output into less: We get the entire song, including duplicate lines, in less: That doesn’t seem to be either the unique lines nor the duplicate lines. If you want to see a list of every duplicated line, as well as an entry for each time a line appears in the file, you can use the -D (all duplicate lines) option. So, why is it showing up in a list of unique lines? In this scenario, the uniq command helps you to print duplicate lines once in the output. This can simply be done with uniq.
It actually discards the lines which are repeated and prints the first adjacent repeated line, which enables us to view the output properly. The line, “I believe I’ll dust my broom,” definitely appears in the song more than once.
The commands will be performed in the order that they are typed. Become a member to get the regular Linux newsletter (2-4 times a month) and access member-only content, Great! Just like duplicate lines, we can filter unique lines … Want to get more out of grep? It is important to note that you cannot use this format to override the original file. uniq filters out the adjacent matching lines from the input file(that is required as an argument) and writes the filtered data to the output file . We have seen the sort command in our previous article, but sorting any file will often result in many duplicate lines adjacent to each other. Comando básico de Linux. Below are a series of examples, beginning with no options. Using -s N option : This is similar to -f N option but it skips N characters but not N fields.
Linux uniq command is used to remove all the repeated lines from a file. In each of these examples, ‘N’ is the count of items that you wish to skip. To use this option, you type the following: The listing contains an entry for each duplicated line. Using -f N option : As told above, this allows the N fields to be skipped while comparing uniqueness of the lines. Likewise, all lines that start with “I’m” are treated as duplicates, even if the rest of the text is different. We type the following to tell uniq to ignore the first field: We get the same results we did when we told uniq to skip three characters at the start of each line. Please use ide.geeksforgeeks.org, generate link and share the link here. October 6, 2020 This is due to the functional limitation I already described. Examples of showing a count of occurrences, showing only repeated lines and ignoring characters and specific fields. However, like many Linux commands, it has a few quirks—which is fine, as long as you know about them. Learn to use the uniq command in Unix and Linux with these practical examples. Writing code in comment? by The fields will be interpreted using the blank space. JavaTpoint offers too many high quality services. Let’s see what uniq makes of it. During his career, he has worked as a freelance programmer, manager of an international software development team, an IT services project manager, and, most recently, as a Data Protection Officer. Check your inbox and click the link to complete signin, Check and Repair Filesystem Errors With fsck Command in Linux, The ln Command in Linux: Create Soft and Hard Links, Beginner's Guide to Analyzing Logs in Linux With journalctl Command.
As you might imagine, that makes this an important concept in learning bash. The uniq command can count and print the number of repeated lines. -u, --unique: it is used to print unique lines.
1. uniq filters out adjacent, matching lines from input file INPUT, writing the filtered data to output file OUTPUT. If no options are specified, matching lines are merged to the first occurrence. If you ran them separately, you could not get these results unless you made a new file and used it to overwrite the content of the original before running your second command. -w, --check-chars=N: It is used to compare not more than N characters in lines. Then when the uniq command is run, it finds only 3 unique lines in the file. This command is designed to work on sorted files.. Purpose : Remove repetitious lines from the sorted ‘input-file’ and send unique lines to the ‘output-file’. 4. If we include the -i (ignore case) option, though, these lines will be treated as duplicates. Wrap up. Some useful command line options of the uniq command are as following: -c, --count: it prefixes the lines by the number of occurrences. We’ll use sort on the file, pipe the sorted output into uniq, and then pipe the final output into less. Just like the field, we can skip characters as well by using the -s option. -i, --ignore-case: It is used to ignore the differences while comparing.
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