how Print previous line ..........

Shell Programming and Scripting
1

HELLO...I wanted to ask you, than sure know unix more than me, as I can obtain the following solution: I have a file with rows of the type:

CIAO COME STAI
PERCHE COME STAI
CIAO COME VA
ALLO CHE FACCIAMO
.................

I would that if in a line is present the word (for example) " CHE " then i can print in video the previous three lines at the word "CHE" obtaining therefore:
CIAO COME STAI
PERCHE COME STAI
CIAO COME VA

As shell i use the KORN SHELL...thanks a lot and sorry for my bad english...

2

Using ksh, bash, ...

#!/bin/ksh
# script
l1=""
l2=""
l3=""
while read line
do
     case "$line" in
        *" CHE"*) echo "$l1"
                     echo "$l2"
                     echo "$l3"
                     l1=""  l2=""  l3=""
                    continue
                    ;;
     esac
     l1="$l2"
     l2="$l3"
     l3="$line"
done

chmod a+rx script
cat somefile | ./script
3 
grep -B3 'CHE' file |grep -v 'CHE'
4

This should do you:

#  awk '
/ CHE / { for (x=1;x<4;x++){print t[NR-x]}}
{t[NR]=$0}
' infile

HTH

5

A Perl solution, just for completeness:

perl -ne 'BEGIN{ @a=("","",""); } print @a if /\bCHE\b/; push @a, $_; shift @a;' infile
6

-B3 is not so usable in all *nix.

grep

  • B3, Gnu extension - my quess.
7 
awk -v v="CHE" '{_[NR]=$0}{for(x=0;x++<NF;)if($x==v){for(y=4;--y;) print _[(NR-y)];printf "\n"}}' file
8

thanks a lot for the help...a last question..it's possible to set the external variable of this case :

awk -v v="CHE" '{_[NR]=$0}{for(x=0;x++<NF;)if($x==v){for(y=4;--y;) print _[(NR-y)];printf "\n"}}' file

from the keybord across the function READ?....

From jmc: next time use code tags [ c o d e ] your code here [ / c o d e ] (remove spaces to make tags work).

9 
read var
awk -v v="$var" '{_[NR]=$0}{for(x=0;x++<NF;)if($x==v){for(y=4;--y;) print _[(NR-y)];printf "\n"}}' file
10

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