How to print a line that matches a pattern?

How to print a line that matches a pattern?

/pattern/s/.*/_/: if current line matches pattern, which means we should print the NEXT following line, then we need to set a indicator to tell sed to print NEXT line, so use s/.*/_/ to substitute all contents in pattern space to a _ (the second command will use it to judge if last line matched the pattern or not).

How to print nth line after matching line?

You can try the -A option with grep, which specifies how many lines after the matching line should be printed. Couple this with sed, and you would get the required lines. Using sed, we delete the from the second line until the fourth. I’m simply adding a deletion of the appropriate lines, before printing { 3,5d ; p }.

How to print a matching line in Perl?

In Perl. the special variable $. is the current line number. So, each time I find a line matching pattern, I print it and save its line number as $c. I then print again when the current line number is 4 more than the one printed previously. You’re essentially doing a find and replace.

How can I make grep print the lines below and above each matching line?

I have to parse a very large file and I want to use the command grep (or any other tool). I want to search each log line for the word FAILED, then print the line above and below each matching line, as well as the matching line.

How can I print all the lines between two lines?

Closed 5 years ago. How can I print all the lines between two lines starting with one pattern for the first line and ending with another pattern for the last line? I guess it was a mistake to mention that this document is HTML. I seem to have touched a nerve, so forget that.

How to print a line following a pattern in SED?

In sed, that could be accomplished like so: Alternatively, grep’s A option might be what you’re looking for. -A NUM, Print NUM lines of trailing context after matching lines. Hope that helps.

Can you substitute last line matching in regex SED?

The last line matching a would not be able to get its all content printed, so you manually print it out in the END block. Before that though, you can substitute the line matching a with whatever you desire. Thanks for contributing an answer to Stack Overflow!

Which is the second line of a sed command?

In this example print second line: The ‘p’ command is preceded by a ‘2’. The number ‘2’ refers to line number two. You can tell sed to perform prints only on a particular line or lines. In this example print 1 to 5 lines:

How are regular expressions used in pattern matching?

A regular expression (sometimes called a rational expression) is a sequence of characters that define a search pattern, mainly for use in pattern matching with strings, or string matching, i.e. “find and replace”-like operations.

How to show all the lines up to the match?

The first option is very similar to what the OP suggested only it makes sure ti show enough lines before context by counting the lines in the file The second option searches the line number of the first match (you could change that as well by changing the inner ‘head’) and than uses head on that number

How does shell script print line from matched line?

When it finds a match it stores the record number ( NR) in the array nr. It also stores the 4th record from NR in the same array. This is done by the nr [NR+4]. Every record ( NR) is then checked to see if it’s present in the nr array, if so the record is printed.

What’s the best way to pattern a print?

Place your pattern piece, right side up, onto the fabric and consider your print. Try and find some areas where the print has sizeable sections to it. The print I used has birds and flowers on it so I was looking to pattern match the largest of those.

When to add a new line before a pattern?

I need to add a new line before any line containing a pattern where we can assume that the pattern is always the first string of the current line. For example To prevent multiple new lines being added (in case of multiple execution) I want to check whether the line before the pattern is empty.

How to add a line in SED if not match?

Opening file for output in the END block replaces the need for utilities like sponge or writing to a temporary file and then mv ing the temporary file to file. The two assignments to array a [] accumulate all output lines into a. if (!f)a [++n]=s appends the new option=value if the main awk loop couldn’t find option in file.

How to show only next line after the matched one?

… the number in the modulo (NR%5) is the added rows by grep (here it’s 3 by the flag -A3), +2 extra lines because you have current matching line and also the — line that the grep is adding. Thanks for contributing an answer to Stack Overflow!

What happens if the first line is the last line in a file?

What it effectively does is it quits if the first line is the last line (i.e. file contains just one line). Remember from one-liner #44 that before quitting sed prints the contents of pattern space. As a result, if the file contains just one line, sed prints it.