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24
votes
4answers
2k views

Reverse grepping

Let's say, I have a really big text file (about 10.000.000 lines). I need to grep it from the end and save result to a file. What's the most efficient way to accomplish task?
20
votes
4answers
785 views

Are Linux utilities smart when running piped commands?

I was just running a few commands in a terminal and I started wondering, does Unix/Linux take shortcuts when running piped commands? For example, let's say I have a file with one million lines, the ...
13
votes
3answers
6k views

How do I minimize disk space usage

One of my machines is the 2GB EeePC Surf, a neat netbook with very limited resources. So limited that right now, I have 22MB free space left. On it, I'm running Arch Linux with the Openbox DE and a ...
6
votes
2answers
405 views

Why is `tac file | grep foo' (piping) faster than `grep foo < <(tac file)' (process substitution)?

This question was motivated by "Reverse grepping", about grepping a huge file from bottom up. @chaos said: tac file | grep whatever Or a bit more effective: grep whatever < <(tac file) ...
4
votes
2answers
1k views

How to install light-weight vim and to be able to efficiently load files into one instance vim?

On my laptop with Ubuntu I'm able to have just one instance of vim, launched with vim --servername VIM After this I'm able to open files from console with vim --remote-silent filename I use ...
4
votes
2answers
152 views

check patterns that don't exist in sqlite

I explained a similar situation with plain text files on Grep huge number of patterns from huge file. Many people there said I should, so now I'm migrating my data to a sqlite database: I have a file ...
4
votes
1answer
474 views

Efficiency of lots of inotify watches or stat calls

I am developing software that will utilize inotify to track changes on a large amount of files (tens to hundreds of thousands of files). I have come up with these ideas: one watch per file one watch ...
2
votes
1answer
228 views

Compare usage of memory by window managers

I'd like to test a few window managers to see which of them takes less memory and CPU in certain time period (so is better choice for older computers). I'd like to make the tests myself (not to read a ...
1
vote
4answers
4k views

Can I access Nth line number of standard output?

Assuming a script that outputs a list of files: $> bash someScript.sh path/to/some/file path/to/the/file/i/want/to/work/with path/to/yet/another/file Now I want to have the second file-path as ...
1
vote
3answers
953 views

Compacting `find` name patterns

I am using find . -name '*.[cCHh][cC]' -exec grep -nHr "$1" {} ';' find . -name '*.[cCHh]' -exec grep -nHr "$1" {} ';' to search for a string in all files ending with .c, .C, .h, .H, .cc and .CC ...
1
vote
1answer
62 views

Do programs access tools like grep, sed, tr, or sort due to their efficiency?

Or it's meaningful only when you are in the command line and want something simple done right away. Are these tools more efficient than a program library?
1
vote
1answer
407 views

Process priority and cpu speed

In some devices the cpu speed is dynamic, being faster when there is more load. I was wondering if it is possible to set nice level or priority of a process so that it does not influence an increase ...
0
votes
1answer
55 views

Check multiple directory properties

I'd like to make this test as fast as possible: (Bash) if [[ -d $directory_path && -r $directory_path && -x $directory_path ]]