Grep the whole body of a function

awkgrepsedvim

Supposing I know that someFile.php contains the definition for someFunction(). How would I go about displaying the whole body of the function in stdout? If I know that the body is 10 lines long then I would use cat someFile.php | grep -A 10 "function someFunction" [1] but in reality the function could be any arbitrary length.

I figured that with sed I could use Vimesque commands such as /function someFunction<Return>/{<Return>% [2] but I can't figure out exactly how to format it. Ideally, the PHPDoc before the function would be output along with the function.

Any help or links to the appropriate fine manual would be appreciated. Thanks!

[1] I know that the cat is redundant, but I find this format easier to read.

[2] Find the function definition, go to the opening brace, go to the close brace

Best Answer

Identify a regular expression that occurs at the end of the function but not in its body. ^} will probably work.

sed –n '/function someFunction/,/^}/p' someFile.php

Obviously, if the PHPDoc before the function begins with some unique string, you would use that rather than /function someFunction/. Otherwise, it’s not so easy; it might be possible with awk.

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Does Unix grep work faster with long or short search terms

Some reference material:

GNU grep uses the well-known Boyer-Moore algorithm, which looks first for the final letter of the target string, and uses a lookup table to tell it how far ahead it can skip in the input whenever it finds a non-matching character.

from Why GNU grep is fast.

The algorithm preprocesses the string being searched for (the pattern), but not the string being searched in (the text). [...] In general, the algorithm runs faster as the pattern length increases.

from Boyer–Moore string search algorithm.

Conclusion: Use longer strings.

Now, a bit of benchmark for fun:

# Initialisation
cd $(mktemp -d) && dd if=/dev/urandom of=random bs=1M count=1000
# Version
grep --v` # grep (GNU grep) 2.9
# Benchmark
(for s in 'short' 'this is not so short and we could even consider this as pretty long'; do for t in {1..10}; do time grep "$s" random; done; done ) 2> result

Results: 0.952s is the average for the short string, 0.244s is the average for the long string.

NB: The length is not the only criterion to be taken into account.

Linux – any way to run grep backwards, i.e. from the end of the file and up

I think the command that will best help you is tac: http://linux.die.net/man/1/tac

As it states:
tac - concatenate and print files in reverse

So you could pipe it to grep and match nnn number of lines before stopping, or something along those lines.

Best Answer

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Does Unix grep work faster with long or short search terms

Linux – any way to run grep backwards, i.e. from the end of the file and up

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