AIX equivalent to GNU grep's -B and -A [print lines after or before matching lines]

Shell Programming and Scripting
1

Hi folks

I am not allowed to install GNU grep on AIX.

Here my code excerpt:

grep_fatal () {
        /usr/sfw/bin/gegrep -B4 -A2 "FATAL|QUEUE|SIGHUP"
}

Howto the same on AIX based machine?

from manual GNU grep

�--after-context=num�
    Print num lines of trailing context after matching lines.
�-B num�
�--before-context=num�
    Print num lines of leading context before matching lines.
2

In this case you might have to write something in awk for example to have a similar functionality.
Althoug there is an old version of GNUgrep in the official IBM Linux toolbox available, just in case you were allowed to install this one.

---------- Post updated at 05:32 PM ---------- Previous update was at 04:30 PM ----------

Without focus on parsing input etc., here a solution in awk how it could look like:

$> cat infile
bla 1
bla 2
bla 3
bla 4
bla 5
bla 6
bla 7
bla 8
bla 9
bla 10


$cat mach.ksh
awk -v direction="$1" -v offset="$2" -v pattern="$3" '

$0 ~ pattern {s=NR; _[NR]=$0; next}
{_[NR]=$0; next}

END{
        if( direction == "B" ){
                x=(s-offset)
                while( s >= x ){
                        print _[x]
                        x++
                }
        }
        if( direction == "A" ){
                x=(s+offset)
                while( s <= x ){
                        print _
                        s++
                }
        }
}' $4

Examples:

$> ./mach.ksh B 2 'bla 5' infile
bla 3
bla 4
bla 5
$> ./mach.ksh A 4 'bla 5' infile
bla 5
bla 6
bla 7
bla 8
bla 9
3

Hi.

You can use a perl work-alike, for example, wgrep, a windowing-grep. It is not a "call-alike" because the options are somewhat different. Here's a sample run on AIX 5.1:

#!/usr/bin/env bash

# @(#) s2       Demonstrate grep-like perl code "wgrep".
# See: http://sysunconfig.net/unixtips/wgrep.txt
# See also "ack": http://betterthangrep.com/

# Infrastructure details, environment, commands for forum posts. 
# Uncomment the export to run script as external user.
# export PATH="/usr/local/bin:/usr/bin:/bin"
set +o nounset
pe() { for i;do printf "%s" "$i";done; printf "%s\n"; }
LC_ALL=C ; LANG=C ; export LC_ALL LANG
pe ; pe "Environment: LC_ALL = $LC_ALL, LANG = $LANG"
pe "(Versions displayed with local utility \"version\")"
c=$( ps | grep "^ $$" | awk '{print $4}' )
version >/dev/null 2>&1 && s=$(_eat $0 $1) || s=""
[ "$c" = "$s" ] && p="$s" || p="$c"
version >/dev/null 2>&1 && version "=o" $p perl ./wgrep
set -o nounset
pe

FILE=${1-data1}

# Display data file:"
cat $FILE

pe
pe " Expected results:"
cat expected-output.txt

pe
pe " Results:"
# ./ack -B 2 -A 1 corge $FILE | 
./wgrep -w2:1 -m corge $FILE |
tee t1

# Check results.

pe
pe " Comparison with desired results:"
if cmp expected-output.txt t1
then
  pe " Passed -- files are same."
else
  pe " Failed -- files differ -- details:"
  diff expected-output.txt t1
fi

exit 0

producing:

$ ./s2

Environment: LC_ALL = C, LANG = C
(Versions displayed with local utility "version")
OS, ker|rel, machine: AIX, 1, 000641284C00
GNU bash 3.00.16
perl 5.6.0
./wgrep wgrep 1.1

foo
bar
baz
qux
quux
corge
grault
garble
warg
fred
plugh
xyzzy
thud

 Expected results:
qux
quux
corge
grault

 Results:
qux
quux
corge
grault

 Comparison with desired results:
 Passed -- files are same.

So you could place wgrep in a directory in your PATH, say ~/bin, and use it directly.

There is a even better work-alike, "ack", that has many of the same options as GNU grep. That is also in perl, and it ran correctly in Linux, hp-ux, and Solaris. Regrettably, it did not run on the AIX 5.1 that I use -- but perhaps it would run on yours.

The URLs in the script comments point to the sites where you can get the code.

If you do not have or know how to create a ~/bin and place it into your PATH, please do some research -- that is a far more general question, but not difficult once one understands the principles involved.

Best wishes ... cheers, drl

4
5

Using PERL -s option will allow you to emulate the GNU grep function as below:-

cat perlgrep

#!/bin/perl -s -wln 

our ( $A , $B , $pattern ) ;

        BEGIN{
                defined $A or $A=0 ; defined $B or $B=0 ; defined $pattern or warn "Pattern Not Exists, kindly insert Pattern $!;" and exit 255 ;
        }

                        $FLINE{$.}=$_ ;

                        /$pattern/ and   $match=$. ;

        END{

                         $b = $match - $B ;
                         $a = $match + $A ;

                while ( $b < $match) {
                        print $FLINE{$b} ;
                        $b++ ;
                }

                print $FLINE{$match} ;

                while ( $a > $match ) {
                        print $FLINE{++$match};

                }
        }

in command user prompt write the below:-

bash-3.00$ chmod u+x perlgrep
bash-3.00$ perlgrep -A=2 -B=4 -pattern='FATAL|QUEUE|SIGHUP' infile.txt

:D:D:D;);):wink: