OS/2 grep had a great feature where it would show you n lines BEFORE the search item was found. Is there an equivalent in unix anywhere?

Question

Solaris would be preferable, but I'll take linux or something I can compile. Does such a beast exist?

score 19 · Answer 1 · answered Oct 20 '11 at 16:19

19

As far as GNU grep go, this will show you the number of lines before the match:

# grep -B number

Equivilent for after:

# grep -A number

You can download GNU Grep here: http://www.gnu.org/s/grep/

answered Oct 20 '11 at 16:19

Kvisle

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2

And `-C` combines both `A` and `B` in one flag. – Daenyth Oct 20 '11 at 19:15

score 6 · Accepted Answer · answered Oct 20 '11 at 16:36

6

You can get GNU grep and it's dependencies for Solaris from sunfreeware.com either as a binary download in pkg format which installs in /usr/local/bin or as a source package.

answered Oct 20 '11 at 16:36

user9517

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score 2 · Answer 3 · answered Oct 20 '11 at 18:09

A small awk script will also work:

#!/usr/bin/awk -f
BEGIN { context=3; }
{ add_buffer($0) }
/pattern/ { print_buffer() }
function add_buffer(line)
{
    buffer[NR % context]=line
}
function print_buffer()
{
    for(i = max(1, NR-context+1); i <= NR; i++) {
        print buffer[i % context]
    }
}
function max(a,b)
{
    if (a > b) { return a } else { return b }
}

replace /pattern/ with the actual regular expression or pattern to search for.

OS/2 grep had a great feature where it would show you n lines BEFORE the search item was found. Is there an equivalent in unix anywhere?

3 Answers3