Why sed Separator (Delimiter) Replacement Not Working with p Command?
Preamble
sed is a powerful stream editor. It can be used to perform various text editing tasks, including searching, replacing, and deleting text. The s command is used to replace text, and the p command is used to print text.
However, there is a caveat when using the s and p commands together. If the delimiter used in the s command is the same as the delimiter used in the p command, the p command will not work as expected.
Address Range and Address for Commands
The reason for this behavior is that the s and p commands are executed in two different passes. The s command is executed first, and then the p command is executed.
When the s command is executed, it replaces all instances of the specified delimiter with the specified replacement text. This means that when the p command is executed, the delimiter used in the s command is no longer present in the text.
As a result, the p command will not be able to find the delimiter and will not print the text as expected.
Solution
To fix this issue, you need to use a different delimiter for the s and p commands. For example, you can use a backslash \ as the delimiter for the s command and a different character, such as a pipe |, as the delimiter for the p command.
Example
$ echo "This is a test" | sed -e 's/ /_/g' -e 'p|cat'
This_is_a_test
In this example, the s command uses a space as the delimiter, and the p command uses a pipe as the delimiter. This allows the p command to print the text correctly.