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nl:tldr:6b4b1
The command nl -b p'FooBar[0-9]' ${filename}
is used to number the lines of a text file and display only the lines that contain the pattern "FooBar" followed by a digit (0-9). Here is a breakdown of each component of the command:
-
nl
: This is the command itself, which stands for "number lines." It is used to display line numbers alongside the contents of a text file. -
-b p
: This is an option used with thenl
command. It stands for "body numbering format" and specifies that only non-empty lines in the file should be numbered. -
'FooBar[0-9]'
: This is a regular expression pattern that is enclosed in single quotes. It specifies the pattern to match in each line of the file. In this case, it matches the string "FooBar" followed by any digit (0-9). -
${filename}
: This is a placeholder for the actual name of the file on which thenl
command will be executed. It is typically replaced with the name of the file or a variable containing the file name.
So, when this command is executed, it will number the lines of the specified file (${filename}
) and only display the lines that contain the pattern "FooBar" followed by a digit.