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I am new to Linux and going through some tutorials and samples. I created a file called test and put alex and alexander in it. I'm trying to find instances of just alex.
If I do grep alex * I get the error:
grep: find: Is a directory.
If I do cat test | grep alex then I get (as expected)
alex
alexander (with alex in red)
Why does the first cause an error, and the second produce expected results?
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To Search Subdirectories To include all subdirectories in a search, add the -r operator to the grep command. This command prints the matches for all files in the current directory, subdirectories, and the exact path with the filename.
Searching RecursivelyThe command will use grep , the -r flag, the pattern/string you want to search for, and the path of the directory to search in. You can see that the command returned every line that matched the pattern in both the poem and story text file.
Conclusion – Grep from files and display the file name grep -n 'string' filename : Force grep to add prefix each line of output with the line number within its input file. grep --with-filename 'word' file OR grep -H 'bar' file1 file2 file3 : Print the file name for each match.
The ls command is used to list files or directories in Linux and other Unix-based operating systems. Just like you navigate in your File explorer or Finder with a GUI, the ls command allows you to list all files or directories in the current directory by default, and further interact with them via the command line.
If you want to search all the files in a directory with grep, use it like this: There is a problem with it. It only searches in all the files in the current directory. It won't search in the subdirectories. You can make grep search in all the files and all the subdirectories of the current directory using the -r recursive search option:
How to use grep. Without passing any option, grep can be used to search for a pattern in a file or group of files. The syntax is: grep '<text-to-be-searched>' <file/files>. Note that single or double quotes are required around the text if it is more than one word. You can also use the wildcard (*) to select all files in a directory.
grep stands for Globally Search For Regular Expression and Print out. It is a command line tool used in UNIX and Linux systems to search a specified pattern in a file or group of files.
If you have a bunch of text files in a directory hierarchy, e.g, the Apache configuration files in /etc/apache2/ and you want to find the file where a specific text is defined, then use the -r option of the grep command to do a recursive search.
If you want to grep phrase from specific file use:
# grep "alex" test
In case you use grep alex * it will search through all files inside the current work directory. In case subdirectory will be met it will tell you something like grep: find: Is a directory
If you want to perform a recursive search use -r key. For example
# grep -r "alex" /some/folder/
In this case all files and files inside subdirectories from /some/folder/ will be checked.
And you can always use man grep.
74
The correct answer would be:
grep -d skip alex /etc/*
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