Bash – How to read certain lines after a find some text

bashshell

How i can read a certain number of lines after find some text?

Eg.:

Best Answer

An awk solution:

$ awk '$0 == "UNIX" {i=1;next};i && i++ <= 2' file
Test 5
Test 6

Explanation

/^UNIX$/{i=1;next}: if we see UNIX, we set variable i = 1, processing to next input.
If variable i is set (meaning we saw UNIX), i && i++ <= 2 only evaluated to true value in next two lines after UNIX, causing awk performed default action print $0.
Before seeing UNIX, i was not defined and begin at 3rd line after UNIX, i had a value greater than 2, which make expression i && i++ <= 2 evaluated to false, causing awk do nothing.

Related Solutions

Bash – how to execute lines coming from a grep result

Assumptions:

you have control over this file and are not in danger of malicious code
you want to set these variables your current shell

You could redirect your commands to a temp file and execute that:

tmp=$(mktemp)
{
    grep somedir INSTALLFILE
    grep 'export PERL5LIB' INSTALLFILE
} > "$tmp"
. "$tmp"

Or you could evaluate the results

eval "$(grep somedir INSTALLFILE)"
eval "$(grep 'export PERL5LIB' INSTALLFILE)"

Updating an old answer. What I would do today is use a process substitution:

source <(
    grep somedir INSTALLFILE
    grep 'export PERL5LIB' INSTALLFILE
)

Shell – Extract Middle Section of Lines in a Text File

If you want not to get messed up but still do it using tail and head, there is a useful way of invoking tail using a line-count from the beginning, not the end:

tail -n +4001 yourfile | head -4000

... But a better, automatic tool made just for splitting files is called... split! It's also a part of GNU coreutils, so any normal Linux system should have it. Here's how you can use it:

split -l 4000 yourInputFile thePrefixForOutputFiles

(See man split if in doubt.)

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Related Solutions

Bash – how to execute lines coming from a grep result

Shell – Extract Middle Section of Lines in a Text File

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