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grep_6 - [<[> < Up >[Top[Contents[Index 6 Usage Here is an...

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[ < ] [ > ] [ << ] [ Up ] [ >> ] [ Top ] [ Contents ] [ Index ] [ ? ] 6. Usage Here is an example shell command that invokes GNU grep : grep -i 'hello.*world' menu.h main.c This lists all lines in the files ` menu.h ' and ` main.c ' that contain the string ` hello ' followed by the string ` world '; this is because ` .* ' matches zero or more characters within a line. See section Regular Expressions . The ` -i ' option causes grep to ignore case, causing it to match the line ` Hello, world! ', which it would not otherwise match. See section Invoking grep , for more details about how to invoke grep . Here are some common questions and answers about grep usage. 1. How can I list just the names of matching files? grep -l 'main' *.c lists the names of all C files in the current directory whose contents mention ` main '. 2. How do I search directories recursively? grep -r 'hello' /home/gigi searches for ` hello ' in all files under the directory ` /home/gigi '. For more control of which files are searched, use find , grep and xargs . For example, the following command searches only C files: find /home/gigi -name '*.c' -print | xargs grep 'hello' /dev/null This differs from the command: grep -r 'hello' *.c which merely looks for ` hello
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