Help with a simple script using awk

Shell Programming and Scripting
1

I need a hand with this simple script,
in Unix i have a variable called portal:
$ echo $portal
chu0
when i use awk this variable is not recognized. How can i make awk recognize and print the value of this variable, since the output is not shown i.e.

awk '
BEGIN {printf("%4s\t%14s\n", "Portal:", portal)}' listacdrs
output:Portal:
Thnaks.

2

Once you enter awk, you cannot use the shell variables directly using $portal or some such. This is because awk has no access to shell variables.

You can pass variables to awk using the '-v' switch. Something like this:

nawk -v a=$a '{print a}' filename

The above code serves no purpose other than to show how a shell variable can be passed to awk. Note that the original Solaris awk does not support this, so with Solaris, you have to use nawk.

3

You can also define the variable in the following way :

awk '{print a}' a=$a filename

The difference is that in that case the variable a is not define in the BEGIN clause.

The script

awk -v v_var='v_option' \
    'BEGIN  { printf("BEGIN v_var=%s f_var=%s\n", v_var, f_var)}
     FNR==1 { printf("FILENAME=%s v_var=%s f_var=%s\n", FILENAME, v_var, f_var)}
     END    { printf("END   v_var=%s f_var=%s\n", v_var, f_var)}' \
     f_var='files_1_2' file1 file2 \
     f_var='file_3'    file3

gives the output :

BEGIN v_var=v_option f_var=
FILENAME=file1 v_var=v_option f_var=files_1_2
FILENAME=file2 v_var=v_option f_var=files_1_2
FILENAME=file3 v_var=v_option f_var=file_3
END   v_var=v_option f_var=file_3

Jean-Pierre.

4

Actually, u can use shell variables inside awk.
for e.g.

u have the file abc which has the folloing contents :

abc def ghi
jkl mno pqr

u need to print the 3rd column
create the shell variable
x=3

then

awk '{print $'$x'}' abc

u'll get the required output. what u need to do is to switch off quoting before $x so that the shell can evaluate it (n return 3) n then switch it on again.

so in ur case, simply, instead of portal, write '$portal'