Shell Programming and Scripting

Example:
O o x
[

2 A X
3 B X
4 C X
5 D X
6 E Z
7 F Z
a b c 12d
]

What I would like to do is to rename the first column of the above file without affecting the format. The output should look like the following:

Output:
O o x
[

1 A X
2 B X
3 C X
4 D X
5 E Z
6 F Z

a b c 12d
]


#! /bin/ksh

cd $HOME/lib/.Lee

#nl = no. of lines.
nl=`grep 'X' ex | wc -l`

#ln = line no.
ln=1
$1=NR
until [[ "$ln" = "$nl" ]]; do
awk '{$1 = NR; print}' ex
ln=ln+1
done

The above script affects the format and the results keep on and on and on.

Code:

awk -v no=1 ' /\[/,/\]/ { if ( $0 ~ "^[0-9]+ " ) { sub("^[0-9]+ ",no" ");no++}}; 1 ' filename

anbu can we have some awk code explanation..I am confused..but I like this topic

thanks in advance

/\[/,/\]/ { ... } This block is executed for lines between [ and ]

$0 ~ "^[0-9]+ " Checks whether first field is a number

sub("^[0-9]+ ",no" ") If above condition is true replace first field by the value in variable "no" and increment the variable "no"

1 which means true and prints the line

thanks for nice explanation..

Thanks for the reply. I tried using the script you gave but showed the following messages:

awk: syntax error at source line 1
awk: bailing out at source line 1


So, I tried few other things but gave the same results. What I want to do exactly is to renumber only the first column where X are found.

Regards.

Use nawk to avoid this error.

Do you mean the X in third field? Then try this

Code:

nawk -v no=1 ' /\[/,/\]/ { if ( $0 ~ "^[0-9]+ " && $3 == "X"  ) { sub("^[0-9]+ ",no" ");no++}}; 1 ' filename