![]() ![]() Let's say that you wanted to use the 'grep' command to find all lines in this file that contain the word 'Hello' followed by the word 'World'. Here is a file containing a few lines of text that we'll place inside the file 'hello.txt': Hello World. Therefore, if you try to do a grep search like this, you'll be waiting a long time (forever). In other words, it's waiting for you to type in some text by hand so it can search it for your term. In this case, grep will just sit there and do nothing because it's waiting for you to type some input (until CTRL+d is pressed) since nothing was fed in from stdin. Or, directly from stdin like this when no files are specified: echo " something " | grep " test "Ī common mistake is to forget to specify a file name at all when issuing a grep search when there is no input from stdin: grep " test " The grep command can accept input from two different methods: 1) From one or more files, like this: grep " test " file.txt (Added on ) By popular demand, many people suggested that I add this item as #0 to this list. The root causes of these mistakes are: Not knowing what flavour of regular expression that grep is currently using (and/or not understanding what features that flavour supports) Not considering the escaping rules of your shell Issues with character encodings. I have chosen to document these mistakes in detail because they are mistakes that beginners are very likely to make at some point, but also to not be able to debug on their own. In this article, I'll discuss 5 very confusing mistakes that have caused me to waste significant amounts of time when using the command-line tool known as 'grep' to search for things. ![]() Grep -l -r -include "*.js" "FIRSTWORD" * | xargs grep -L "SECONDwORD"ĭc0fd654-37df-4420-8ba5-6046a9dbe406 grep -l -r -include "*.The Most Confusing Grep Mistakes I've Ever Made - By Robert Elder Introduction grep -l -r -include "*.js" "FIRSTWORD" * | xargs grep "SECONDwORD" Get the first matched files from grep command and get all the files don't contain some word, but input files for second grep comes from result files of first grep command. Grep -RH "cats" /home/adam/Desktop/TomAndJerry #absolute directoryĪ short introduction to symbolic links, for anyone reading this answer and confused by my reference to them: If you want to find all mentions of the word cat in the directory /home/adam/Desktop/TomAndJerryĪnd you're currently in the directory /home/adam/Desktop/WorldDominationPlotĪnd you want to capture the filename but not the line number of any instance of the string "cats", and you want the recursion to follow symbolic links if it finds them, you could run either of the following grep -RH "cats". So if you want to find all files containing Darth Vader in the current directory or any subdirectories and capture the filename and line number, but do not want the recursion to follow symbolic links, the command would be grep -rnH "Darth Vader". Since you're trying to grep recursively, the following options may also be useful to you: -H: outputs the filename with the line If you want to follow symbolic links as well as actual directories (be careful of infinite recursion), grep -R "thing to be found" directory ![]() If you only want to follow actual directories, and not symbolic links, grep -r "thingToBeFound" directory Vendor/klaussilveira/gitter/lib/Gitter/Client.php:176: return $this->hidden Vendor/klaussilveira/gitter/lib/Gitter/Client.php:170: * Get hidden repository list Vendor/klaussilveira/gitter/lib/Gitter/Client.php:20: protected $hidden Tests/InterfaceTest.php:32: $options = array(self::$tmpdir. ![]() Src/GitList/Provider/GitServiceProvider.php:21: $options = $app Src/GitList/Application.php:43: 'git.hidden' => $config->get('git', 'hidden') ? $config->get('git', 'hidden') : array(), I can get: /home/vonc/gitpoc/passenger/gitlist/github #grep -include="*.php" -nRHI "hidden" * This is equivalent to the -binary-files=without-match option.Īnd I can add ' i' ( -nRHIi), if I want case-insensitive results. Process a binary file as if it did not contain matching data Read all files under each directory, recursively this is equivalent to the -d recurse option. (Note: phuclv adds in the comments that -n decreases performance a lot so, so you might want to skip that option) -R, -r, -recursive Prefix each line of output with the line number within its input file. Recurse in directories only searching file matching PATTERN. That includes the following options: -include=PATTERN (As noted by kronen in the comments, you can add 2>/dev/null to void permission denied outputs) I now always use (even on Windows with GoW - Gnu on Windows): grep -include="*.xxx" -nRHI "my Text to grep" * ![]()
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