Passing Parameters to an Executable Awk Script

[oldwhtman]

I've spent as couple hours searching in vain for an example of how to pass parameters to an executable awk script. Can anyone lead me to such an example? I tried the following syntax:

#!/bin/gawk -v "var=$1" -f
begin {
print "var=" var
}

Using the command:

>myscript.awk <value> <file-name>

but it says 'var is not a valid variable name.

I've tried everything I could think of that seemed logical, but nothing works.

 

[feherke]

Hi

The shebang line is not a full featured command line.

Use [tt]ARGC[/tt] and [tt]ARGV[/tt] to access the command line parameters :

[gray]#!/usr/bin/gawk -f[/gray]

[b]BEGIN[/b] {
  [b]print[/b] [green][i]"I got"[/i][/green], ARGC - 1, [green][i]"parameters :"[/i][/green]

  [b]for[/b] (i = 1; i < ARGC; i++)
    [b]print[/b] [green][i]" -"[/i][/green], i, [green][i]"="[/i][/green], ARGV[i]
}

[blue]master #[/blue] .myscript/.awk Hello World!
I got 2 parameters :
 - 1 = Hello
 - 2 = World!

( Note that [tt]ARGV[0][/tt] is the process' name. )

Feherke.
feherke.ga

 

[oldwhtman]

Thanks, feherke.ga, but this does not work when processing a text file. My example omitted the detail procesccing. Your example works because there is no 'detail' processing of a text file. My script tries to interpret all parameters as files to be processed.

 

[PHV]

My script
Which script ?

Hope This Helps, PH.
FAQ219-2884
FAQ181-2886

 

[oldwhtman]

The script fragment I wrote in my original post. However, thinking it wasn't relevent, I left out the detail block, which apparently changes how the parameters are interpreted. Here's my example again with detail processing:

#!/bin/gawk -v "var=$1" -f
begin {
print "var=" var
}
{
print
}

 

[feherke]

Hi

Then you have to come up with a syntax for calling your script, then implement parameter parsing according to your rules.

For example, I say that my script :
[ul]
[li]will handle values, signaled by preceding them with a "-v" option[/li]
[li]will handle filenames, not signaled in any way[/li]
[/ul]

Then I implement it as :

[gray]#!/usr/bin/gawk -f[/gray]

[b]BEGIN[/b] {
  [b]print[/b] [green][i]"I got"[/i][/green], ARGC - 1, [green][i]"parameters :"[/i][/green]

  valuefollows = 0
  [b]for[/b] (i = 1; i < ARGC; i++) {
    [b]print[/b] [green][i]" -"[/i][/green], i, [green][i]"="[/i][/green], ARGV[ignore][i][/ignore]
    [b]if[/b] (valuefollows) {
      [b]print[/b] [green][i]"( this was a value, so removed it from further processing )"[/i][/green]
      [b]delete[/b] ARGV[ignore][i][/ignore]
      valuefollows = 0
    } [b]else[/b] [b]if[/b] (ARGV[ignore][i][/ignore] == [green][i]"-v"[/i][/green]) {
      [b]print[/b] [green][i]"( -v detected, so the next one is a value )"[/i][/green]
      [b]delete[/b] ARGV
      valuefollows = 1
    } [b]else[/b] {
      [b]print[/b] [green][i]"( nothing special, so kept for further processing )"[/i][/green]
    }
  }
}

[b]BEGINFILE[/b] {
  [b]print[/b] [green][i]"Starting file"[/i][/green], FILENAME, [green][i]":"[/i][/green]
}

{
  [b]print[/b] [green][i]"Line"[/i][/green], FNR, [green][i]"="[/i][/green], $0
}

[blue]master #[/blue] date | ./awk.awk -- -v Hello txt.txt -v World! -
I got 6 parameters :
 - 1 = -v
( -v detected, so the next one is a value )
 - 2 = Hello
( this was a value, so removed it from further processing )
 - 3 = txt.txt
( nothing special, so kept for further processing )
 - 4 = -v
( -v detected, so the next one is a value )
 - 5 = World!
( this was a value, so removed it from further processing )
 - 6 = -
( nothing special, so kept for further processing )
Starting file txt.txt :
Line 1 =     February 2014
Line 2 = Su Mo Tu We Th Fr Sa
Line 3 =                    1
Line 4 =  2  3  4  5  6  7  8
Line 5 =  9 10 11 12 13 14 15
Line 6 = 16 17 18 19 20 21 22
Line 7 = 23 24 25 26 27 28
Line 8 =
Starting file - :
Line 1 = Fri Feb 28 17:12:45 EET 2014

Long story short : if you not want a parameter to be processed as input file name, remove it before Awk tries to handle it as such.

Feherke.
feherke.ga

 

[oldwhtman]

Thanks again for your time and promptness in helping me . But your solution seems a bit complex, but informative. I didn't realize I could delete ARGV. That is good to know. However, I think a simpler solution for my purposes would be to utilize the fact that a parameter containing the "=" sign is not considered to be a file name by gawk. I discovered this early on. So I can use ARGV to get a string, such as "num=3" in the BEGIN block and then extract the number 3 from that string. But it would be nice, if the developers would allow the following:

#!/usr/bin/gawk -v num=$1 -f

So I could just execute:
myscript 3 file.txt

For some odd reason gawk says variable 'num' is not legal. Doesn't make any sense to me.

Thanks again. You've been very helpful.

 

[LKBrwnDBA]

If you continue using your erroneous script, you will get no-where.
Re-read ferherke's post about:

The shebang line is not a full featured command line.

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The person who says it can't be done should not interrupt the person doing it. -- Chinese proverb