3/29/2023 0 Comments Grep unique![]() The -s option in the second command stabilizes the sort, ensuring that identical lines are output in the same order in which they occurred in the input. Thompson Geller $ sort -fs names-list.txt ![]() The default sorting algorithm used by sort is unstable because lines judged to be identical may be printed out of order with regards to their original place: $ cat names-list.txt The -f option for sort forces sort to ignore the case of a letter when ordering lines. Gil Watson $ sort -R names-list.txt -random-source=/dev/urandomĪaron Smith Ignore Case when Reordering with sort Consider the output of the following commands: $ sort -R names-list.txt -random-source=/dev/random If you prefer, sort can scramble a list using the system’s random number generator /dev/random or pseudo-random number generator /dev/urandom. Identical lines are always printed adjacently to each other. The pseudo-random order is determined by using a cryptographic hash of the contents of lines, which produces a fast shuffle. Sort can scramble the order of lines using the -R option: $ sort -R names-list.txt You can reverse the order of sort output with the -r option, as follows: $ sort -r names-list.txtĪaron Smith Scramble List Order with sort Capital letters are ordered after lower case letters. Sort simply reorders the list alphabetically and outputs the sorted list to the standard output. Joni Governor Reorder Lists with sort $ sort names-list.txt The examples in this section will use the following text file as an input: Because uniq only removes identical adjacent lines, it is often used in conjunction with sort to remove non-adjacent duplicate lines. The uniq command takes input and removes repeated lines. Here, the sorted output is written to the ~/retired-roster.txt file. To write this content to a file, redirect the output as in the following example: grep -i "retired" ~/roster.txt | sort > ~/retired-roster.txt In the default configuration, this sort prints the output on the terminal. These results are sent to sort, which reorders this output alphabetically. This uses grep to filter the ~/roster.txt file for the string retired, regardless of case. ![]() Sort also accepts input from other commands as in the following example: grep -i "retired" ~/roster.txt | sort sort commands take the following format: sort ~/roster.txt Sorted text is sent to standard output and printed on the terminal unless redirected. The sort command accepts input from a text file or standard output, sorts the input by line, and outputs the result. Though narrow in their focus, both of these tools are useful in a number of different command line operations. The uniq command takes a list of items and removes adjacent duplicate lines. ![]() The sort command takes a list of items and sorts them alphabetically and numerically. You see that this don't return from /etc/httpd/conf/httpd.The Linux utilities sort and uniq are useful for ordering and manipulating data in text files and as part of shell scripting. So you can apply this pattern for searching "Apache" string in files from /etc directory-looking only in files below this main directory. To get rid of error redirect to /dev/null for example grep PATH ~/.* 2>/dev/null Using grep PATH ~/.* you'll see all occurrence, including line with searching keyword. So this search for string "PATH" listing name of the files below the user's home directory, only for files that start with a dot. You can think like this, for example using grep. How can I search all the files in a directory (and not its subdirectories) using grep? Why does using wildcards to specify multiple files to search in for work with. Please give me an explanation on the workings of grep that would explain the behavior of commands in (2).Įdit: Let me be more specific. I believe that this is what grep does when you pass a directory to it in place of a file. Why am I not being able to use grep on a directory, as in (1), when I should be able to? I've seen that done in plenty examples on the Internet.Įdit: When I say "using grep on a directory", I mean "search in all the files in that directory excluding its subdirectories". I tried using the -s option, but to no avail. Only the errors are printed, I don't get the matching lines. Grep "string" * gives me the errors: grep: data: Is a directory Next, I tried running grep on multiple files. Is supposed to be able to do this, I've read, but it gives me the error: I want to search for a string of text in all files in a directory (and not its subdirectories I know the -r option does that, but that is not what I want).
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