Shell Programming and Scripting

consider a file with the following format: a header row with

colon-separated field names, and data rows with colon-separated values. for

example:



AGE:EYES:HAIR

32:BLUE:BLONDE

54:BROWN:BROWN



write a script, named extract_columns, that prints out the values

corresponding to the fields specified by the user on the command line, in the

order specified by the user. suppose that the above file was named data.txt.

then typing:



%> extract_columns data.txt EYES



should produce



BLUE

BROWN



and typing:



%> extract_columns data.txt HAIR AGE



should produce



BLONDE 32

BROWN 54



the script should die with a warning if the user requests a field that does

not exist in the data file. The script should run on any input file that

conforms to the format described above.

Is this for a homework assignment?

Hi,

Hope this one can help you.

input(a):

Code:

AGE:EYES:HAIR

32:BLUE:BLONDE

54:BROWN:BROWN

code(b):

Code:

nawk -v c="$*" 'BEGIN{FS=":"
}
{
if (NR==1)
        for (i=1;i<=NF;i++)
                if (index(c,$i)!=0)
                        a[i]=i
if (NR>1)
{
        for (j in a)
        printf $j " "
        print ""
}
}' a

output:

Code:

sh b EYES:

BLUE

BROWN

sh b AGE HAIR:

BLONDE 32

BROWN 54

Hi, here is one script, bit lengthy one..

#!/bin/sh
i=1
flag=0
IFS=:
for x in `grep "$1" file`
do
if [ "$x" == "$1" ]
then
flag=1
break;
fi
i=`expr $i + 1`
done

if [ $flag -eq 1 ]
then
awk -F':' "{ print $`echo $i` }" file
else
echo "string not available"
exit 1
fi

Note: It has one disadvantage, the grep is case sensitive, so the user should feed the correct case of string to search for in the file.

#!/usr/bin/ksh

case $1 in

AGE) cat filename |cut -d: -f1
;;
EYES) cat filename |cut -d: -f2
;;
HAIR) cat filename |cut -d: -f3
;;
esac