Using awk grep sed
grep does not alter a file, it only finds matches while awk and sed are text processors.
awk is mostly used for data extraction and reporting. sed is a stream editor. Each one of them has its own functionality and specialties.
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sed
Things that you can accomplish using RegEx within the Vi editor on text files can also be accomplished at the command line with sed.
The most basic form is to use sed as a simple search and replace.
sed 's/windows/linux/'
example: process text file by removing blanks, unwanted lines, and duplicates
Get rid of all lines of text containing numerical stats
sed -i '/[0-9]/d' Razor-Fen.txt
Get rid of all empty lines containing no characters
sed -i '/^\s*$/d' Razor-Fen.txt
Get rid of all duplicate lines
sed -i '$!N; /^\(.*\)\n\1$/!P; D' Razor-Fen.txt
grep
example: rgrep
rgrep is grep -r or recursive grep
If you want to search all text files within all subfolders for a particular matching string, the syntax might not be what you would think
For example, rgrep string *.txt will not search though all text files under the current directory, the correct syntax would be:
rgrep -s string --include \*.txt
Here is an example that searches for multiple specific types
rgrep -i --include \*.h --include \*.cpp CP_Image ~/path[12345]
awk
The awk utility operates on a line-by-line basis and iterates through the entire file and is therefore useful for changing data files and generating reports.
This command utility is extremely useful for formatting text to the screen or for print. You can process huge log files to output a readable report that you can better utilize.
Format:
awk '/pattern/ { action_to_take; another_action; }' file_to_parse
By default Awk behaves like 'cat' in that it prints every line of data from the specified file.
awk '{print}' inventory.txt
picking out specific lines in the data or text file
We might have a space separated data file or a text file with lines of composition, either way, we can pick out and print entire lines of text if a single word in the line is matched.
awk '/plumbing/ {print}' inventory.txt
In the inventory file there is a second column of text that specifies the department of the listed supply item. Only lines from the text file will be printed if the item is in the plumbing department. Alternatively, if it is a composition, only lines where the word 'plumbing' is matched will be printed.
