Pipes and Filters

Re:Pipes and Filters by unhammer on Wednesday September 17, 2014 @04:13AM (#8329018)

Also, the cat makes for faster testing. I tend to start out with e.g.

    head bigfile.1.txt | grep | awk | stuff

and refine things, and when output looks right, it's a simple "Ctrl+A Meta+D cat RET" to run it on the full output. Or vice versa if I suddenly want to go back to testing part of bigfile (or exchange the cat for "grep something").

If I want to change that to "< bigfile.1.txt", I have to "Ctrl+A Meta+D < Meta+F Meta+F Meta+F Ctrl+D Ctrl+D" – the extra keypresses are to delete the first "|" symbol. And if I suddenly want to change it back to head or grep, I have to reinsert the | (also I often by habit do Meta+D instead of Ctrl+D at the beginning of the line, which doesn't work as intended if the first token is "<" instead of "cat").

Those useless cats are quite handy when doing a lot of shell work.

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Re:Pipes and Filters by JetSpiegel on Wednesday September 17, 2014 @05:11AM (#8329191)

You can use <bigfile.txt head | grep | awk

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Re:Pipes and Filters by unhammer on Wednesday September 17, 2014 @09:39AM (#8329858)

So if I want to change that to the whole file, I "just" have to Ctrl+A Meta+F Meta+F Meta+D Ctrl+D Ctrl+D RET. That's not really an improvement – especially since it depends on how many dots or similar are in the filename.

Also, that's a Useless Use of head, since grep has the option "-m10"

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Re:Pipes and Filters by JetSpiegel on Wednesday September 17, 2014 @02:13PM (#8331450)

grep -m "Stop reading a file after NUM matching lines", while head -10 takes the first 10 lines and searches on them. Different things.

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Re:Pipes and Filters by unhammer on Wednesday September 17, 2014 @04:34PM (#8332224)

doh! you're right, I wasn't thinking :-)

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