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joplin notion extension/linux/Snippets/sed example.md

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+sed example
+
+
+theory
+grep is powerful along with other unix tools like cut xargs head less etc.
+awk goes line by line in a file/stdin giving you all the words in variables with like $1 $2 $3 which you can use however you want
+
+To achieve this using `sed` (Stream Editor), you can use a regular expression pattern to match the text you want to modify and then replace it with the desired output.
+
+Assuming you want to remove the `.md` from occurrences of patterns like `(sdusyd.md)` within a file and considering your example, we use the following `sed` command:
+
+```bash
+sed 's/\(([^)]*)\).md/\1/g' file.txt
+```
+
+Here's a breakdown of the command:
+
+- `sed`: The command to call Stream Editor.
+- `s/pattern/replacement/`: The substitute command, where `pattern` is the regex pattern you are looking to match, and `replacement` is the text you want to use to replace the matched pattern.
+- `\(([^)]*)\).md`: This is the regex pattern we are matching. 
+  - `\(`: Matches the literal character "(".
+  - `([^)]*)`: Matches and captures any character except `)` zero or more times. This corresponds to your `<string>`.
+  - `\)`: Matches the literal character ")".
+  - `.md`: Matches the string `.md` that we intend to remove.
+- `\1`: Refers to the first captured group from the match. In this case, it's the string matched by `([^)]*)`, which is `<string>`.
+- `g`: Global flag to perform the replacement for all occurrences within a line.
+- `file.txt`: The file in which the replacements should occur.
+
+
+For example, if `file.txt` contains:
+
+```text
+Some text (sdusyd.md) with markdown files and another (anotherfile.md).
+```
+
+After running the command, it will output:
+
+```text
+Some text (sdusyd) with markdown files and another (anotherfile).
+```
+
+**Note**: If you want to directly modify the file (instead of just outputting the modified text to the terminal), you can use the `-i` option for in-place editing with `sed`. Just remember to backup your original files before using `-i`, as it overwrites the original file:
+
+```bash
+sed -i 's/\(([^)]*)\).md/\1/g' file.txt
+```
+
+This will change `file.txt` in-place.
+
+- same thing with perl
+  	`perl -pe 's/\(([^()]+)\.md\)/\($1\)/g' file.txt` : this will only print output without modifying file
+	`perl -pi -e  's/\(([^()]+)\.md\)/\($1\)/g' test.txt` : this will modify file too
+	
+	this worked for me
+```bash
+sed -E -i 's/\(([^\)]*)\.md\)/\(\1\)/g' file.txt
+```
+
+&nbsp;
+replicating grep with awk
+`history | awk '/cd/'` will replicate3 `history | grep 'cd'`