How to search and replace in Linux files

[Fli]

Before doing search and replace, backup data.

search and replace in file:
sed -i "s|search|replace|g" file

search and replace in the variable
$variable="$(echo "$variable"|sed "s|search|replace|g")

search and replace only if line contains defined phrase:
sed -i "/Next/ s|#||g" file
(replace # by nothing (remove) on the line that contains Next)

search and replace multiple phrases in file:
sed -i "s|search|replace|g;s|search2|replace2|g"

Preview changes instead of writing them into file:
cat "filename"|sed "s|search|replace|g"

search and replace in all directory files containing username .php:
for file in $(find -A1 /path/to/filesdir/|grep -v "./"|grep ".php");do sed -i "s|search|replace|g" $file;done

NOTES:

backup before doing search&replace

one can use / or other character instead of |

some characters like slash and quotation mark needs to be escaped by backslash, example: sed -i "s|<img src=\"\" \/>|<img src=\"url\" \/>|g" file

[RuskinF]

grep is the most important command to use to replace data in files in Linux.
I will let you know what you can do to use grep command.

grep is a utility for searching for strings through multiple text files. Here I'm invoking it with the following parameters:

R — perform a recursive search, also across symbolic links;
i — case-insensitive search
I — skip binary files. We are working with text, afer all;
l — print results as a simple list of file names. This is needed for the next command.

Apart from that, you need sed.

sed is a glorious Unix utility that transforms text. In the current snippet I'm using it to replace text with the following parameters:

i — replace in file. Remove it for a dry run mode;
s/search/replace/g — this is the substitution command. The s stands for substitute (i.e. replace), the g instructs the command to replace all occurrences.


FunFact: Azure Windows 10 is a virtual desktop based on Azure platform which itself is based on Linux kernel.

[Maja22]

Before doing search and replace, backup data.

search and replace in file:
sed -i "s|search|replace|g" file

search and replace in the https://zumbaliciouscrew.com/en/zumba-online-class/ variable
$variable="$(echo "$variable"|sed "s|search|replace|g")

search and replace only if line contains defined phrase:
sed -i "/Next/ s|#||g" file
(replace # by nothing (remove) on the line that contains Next)

search and replace multiple phrases in file:
sed -i "s|search|replace|g;s|search2|replace2|g"

Preview changes instead of writing them into file:
cat "filename"|sed "s|search|replace|g"

search and replace in all directory files containing username .php:
for file in $(find -A1 /path/to/filesdir/|grep -v "./"|grep ".php");do sed -i "s|search|replace|g" $file;done

NOTES:

backup before doing search&replace

one can use / or other character instead of |

some characters like slash and quotation mark needs to be escaped by backslash, example: sed -i "s|<img src=\"\" \/>|<img src=\"url\" \/>|g" file

When working with text files or variables, search and replace operations are common tasks. The sed command is a powerful tool to accomplish these tasks efficiently. Before making any changes, it’s always important to back up your data to ensure that no information is lost if something goes wrong.

To search and replace text in a file, you can use the sed command. For example, the command sed -i "s|search|replace|g" file will find all occurrences of the word "search" and replace them with "replace" in the specified file. The -i flag ensures the changes are made directly to the file. The s in the command stands for substitution, and the g ensures that all matches in each line are replaced, not just the first one. You can use a character other than | as a delimiter, such as /, depending on the context.

If you need to modify the value of a variable, you can use a similar approach. For instance, the command $variable="$(echo "$variable" | sed "s|search|replace|g")" passes the variable through sed, performs the replacement, and reassigns the updated value back to the variable.

Sometimes, you may want to perform replacements only on lines containing a specific phrase. This can be achieved with a conditional command like sed -i "/Next/ s|#||g" file, which removes the # character only on lines that contain the word "Next."

For more complex tasks, you can perform multiple replacements in a single command. For example, sed -i "s|search|replace|g;s|search2|replace2|g" will replace both "search" with "replace" and "search2" with "replace2" in one go.

To preview changes instead of applying them, you can pipe the file content to sed with a command like cat "filename" | sed "s|search|replace|g". This will display the updated content without modifying the file.

If you need to search and replace text across multiple files, such as all .php files in a directory, a loop can be used. For example:

bash
Copy code
for file in $(find -A1 /path/to/filesdir/ | grep -v "./" | grep ".php"); do
sed -i "s|search|replace|g" $file;
done
This command finds all .php files and applies the replacement to each one.

Finally, be mindful of escaping special characters like slashes (/) and quotation marks ("). For instance, replacing <img src=""/> with <img src="url"/> would require escaping quotation marks: sed -i "s|<img src="" />|<img src="url" />|g" file.

Always remember: backup your data before performing any search and replace operations!