[SOLVED] sed print range from pattern1 to pattern2

porphyry5 · 06-14-2011, 03:38 PM

From a file I want to extract a range of lines by patterns. I've used variations on

Code:

sed -n -e '/^BashNotes/,/^EndOf[A-Za-z]*$/ p' -e '/^EndOf[A-Za-z]*$/ q' Notes

So, I want to extract lines starting from one whose first word is specified, in this case "BashNotes", and ending at the first line consisting of the single word "EndOf...", which in this case would be "EndOfBashNotes".

Either I get no output at all, or it prints from the start of file to the first EndOf..., so the problem has to be with "^BashNotes", e.g. remove the "^" and it accesses an earlier occurrence of "BashNotes" that is in the middle of the first line of the file, and prints to the first occurrence of "EndOf...".

So why should a "^" in the "from" pattern be objectionable, when it is acceptable in the "to" pattern and the "quit" statement?

crts · 06-14-2011, 07:31 PM

Quote:

Originally Posted by porphyry5

From a file I want to extract a range of lines by patterns. I've used variations on

Code:

sed -n -e '/^BashNotes/,/^EndOf[A-Za-z]*$/ p' -e '/^EndOf[A-Za-z]*$/ q' Notes

So, I want to extract lines starting from one whose first word is specified, in this case "BashNotes", and ending at the first line consisting of the single word "EndOf...", which in this case would be "EndOfBashNotes".

Either I get no output at all, or it prints from the start of file to the first EndOf..., so the problem has to be with "^BashNotes", e.g. remove the "^" and it accesses an earlier occurrence of "BashNotes" that is in the middle of the first line of the file, and prints to the first occurrence of "EndOf...".

So why should a "^" in the "from" pattern be objectionable, when it is acceptable in the "to" pattern and the "quit" statement?

Hi,

without some sample data it is hard to guess why it does not work. Maybe some leading spaces? Try

Code:

sed -n -e '/^[[:blank:]]*BashNotes/ ...'

If this does not fix the issue then provide a representative sample file.

porphyry5 · 06-14-2011, 09:35 PM

Quote:

Originally Posted by crts

Hi,

without some sample data it is hard to guess why it does not work. Maybe some leading spaces? Try

Code:

sed -n -e '/^[[:blank:]]*BashNotes/ ...'

If this does not fix the issue then provide a representative sample file.

Has the same result, nothing is returned. There is no leading whitespace. I apologize, I should have mentioned in the first post that my regexes work exactly as expected in a different text editor, kwrite as it happens, but I was thinking I had to have made some syntactical error with sed. I've attached the front end of the file concerned.

crts · 06-14-2011, 10:38 PM

Ok, I see now. Try the following to see the error:

Code:

$ sed -n -e '/^EndOf[A-Za-z]*$/ p' -e '/^EndOf[A-Za-z]*$/ q' Notes
EndOfAwkCommands

As you can see, your RegEx matches 'EnOfAwkCommands' and therefore it quits. Since there 'BashNotes' has not been encountered before - when you use the 'sed' in your initial post - nothing will get printed.
This worked for me:

Code:

sed -n '/^BashNotes/,/^EndOf[A-Za-z]*$/ p' Notes

It printed 624 lines. I am not sure why you want to use the 'q' command.

Reuti · 06-15-2011, 04:47 AM

Depending on the size maybe the q command can save some time (and/or avoid to find any further block of BashNotes/EndOf...).

porphyry5 · 06-15-2011, 08:48 AM

Quote:

Originally Posted by crts

Ok, I see now. Try the following to see the error:

Code:

$ sed -n -e '/^EndOf[A-Za-z]*$/ p' -e '/^EndOf[A-Za-z]*$/ q' Notes
EndOfAwkCommands

As you can see, your RegEx matches 'EnOfAwkCommands' and therefore it quits. Since there 'BashNotes' has not been encountered before - when you use the 'sed' in your initial post - nothing will get printed.
This worked for me:

Code:

sed -n '/^BashNotes/,/^EndOf[A-Za-z]*$/ p' Notes

It printed 624 lines. I am not sure why you want to use the 'q' command.

Thank you very much. You mean that the quit statement gets a match before it ever gets to BashNotes. I was under the impression that the commands proceeded stepwise, that the range match would have to complete before it ever tried the quit test. That was only there to stop it processing any further once it satisfied the range command.

crts · 06-15-2011, 09:06 AM

Quote:

Originally Posted by porphyry5

You mean that the quit statement gets a match before it ever gets to BashNotes.

Yes, that is exactly what happens. If for some reason you want to quit processing after the range has been printed then you can do the following:

Code:

sed -n '/^BashNotes/,/^EndOf[A-Za-z]*/ {p;/^EndOf[A-Za-z]*/q}' Notes

This will execute the 'q' command only when inside the range. Notice, that I removed the 'end of line' marker '$' to accommodate for trailing spaces.

porphyry5 · 06-15-2011, 09:57 AM

Quote:

Originally Posted by crts

Yes, that is exactly what happens. If for some reason you want to quit processing after the range has been printed then you can do the following:

Code:

sed -n '/^BashNotes/,/^EndOf[A-Za-z]*/ {p;/^EndOf[A-Za-z]*/q}' Notes

This will execute the 'q' command only when inside the range. Notice, that I removed the 'end of line' marker '$' to accommodate for trailing spaces.

Thank you again, so one uses {...} to ensure the previous command is satisfied before accessing the commands in the braces. No harm is done by removing either ^ or $, I only use those compound word arrangements for titles and end markers, to distinguish them from regular text, so any range combination can only occur once.