To select lines using character ranges, you can do something like this: $ cut -c1-3 weekdays $ cut -f1 addressesħ610 West Park Drive, Hyattsville, MD 20783 If we asked for the first field without specifying a delimiter, we would see entire lines in any file that is not delimited by tabs. The second (delimited by commas) displays all of the text up to the first comma. The first (delimited by blanks) displays the first field. The two command below show different amounts of each line. Just remember that you need to specify the delimiter if the words or strings are not separated by tabs. You can also use the cut command to select single and multiple words or strings from a file. These are, of course, accounts associated with system services. Notice how many accounts cannot log in because they're assigned the /sbin/nologin shell. To count how many accounts use each of the shells, use a command like this: $ cut -d: -f 7 /etc/passwd | sort | uniq -c The command above selects the 1st and 7th fields. To select to see both login names and assigned shells, try this: To specify a different delimiter, you could add the -d option and use a command like this one, which pulls usernames from the /etc/passwd file: $ cut -d: -f 1 /etc/passwd | head -10 The string -f1-4 would display the first four fields in the file: $ cut -f1-4 cities | head -5 Since the tab character is the default delimiter for the cut command, it easily extracts these fields. To add the city names to your selection, you would select the 2nd and 4th fields. To select a particular field from this file, you might use a command like this that shows the 4th field: The lines in this file look something like what is shown below: $ head -5 cities To illustrate how the cut command works, we'll first run commands using a sample "cities" file that contains details of the largest cities in the US in a tab-separated format. Ihnat, David MacKenzie, and Jim Meyering. There is NO WARRANTY, to the extent permitted by law. This is free software: you are free to change and redistribute it. License GPLv3+: GNU GPL version 3 or later. To check on cut, you can ask about its version like this: $ cut -versionĬopyright (C) 2020 Free Software Foundation, Inc. It works something like awk in that it allows you to select only what you want to see from files, enabling you to pull fields (regardless of the delimiter used), characters or bytes. For example, the first match “ RuntimeException…” is located at line 2 + 6 – 1 = 7 in the app.log file.One surprisingly easy command for grabbing a portion of every line in a text file on a Linux system is cut. Of course, we can get the actual line numbers through this calculation: LINE_NO_BY_GREP + 6 – 1. However, since we piped the tail command’s output to grep, the line numbers reported by the grep command are not the actual line numbers in the original input file. So, let’s execute the command with the -n option: $ tail -n +6 app.log | grep -n 'Exception'Ģ: RuntimeException: File not found: /foo/bar/newFileĤ: TemplateNotFoundException: Template PRETTY not found, loading the default templateĦ: Cleanup job done with IOException: Disk is fullĪs we can see, this time, the command has printed the line numbers of matched lines. For example, this helps us locate the log entries with “ Exception” and take a closer look at the stack trace to analyze the cause. However, sometimes, we would like to execute the grep command with the -n option to print the line numbers of each match. RuntimeException: File not found: /foo/bar/newFileĪs we can see, the command above has solved the problem. Next, let’s execute the grep command on the output above to get the required log entries: $ tail -n +6 app.log | grep 'Exception' Cleanup job done with IOException: Disk is full TemplateNotFoundException: Template PRETTY not found, loading the default template RuntimeException: File not found: /foo/bar/newFile
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