awk - Why can't value of awk variables be passed to external functions ?


 
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# 1  
Old 11-22-2014
awk - Why can't value of awk variables be passed to external functions ?

I wrote a very simple script to understand how to call user-defined functions from within awk after reading this post.

Code:
function my_func_local {
echo "In func $1"
}

export -f my_func_local

echo $1 | awk -F"/" '{for (k=1;k<=NF;k++) {
if ($k == "a" ) {
system("my_local_func $k")
}
else{
print $k
}
}                        
}

I am running with the arguments-:
sh script.sh a/b/c/d/e
The expected output should be-:
Code:
In func a
b
c
d
e

But what I am getting is-:
Code:
In func
b
c
d
e

The value of k is not being passed into the external function when I am calling it from awk. Why is this happening ? How do you rectify this ? I need the function to be called within awk because what I am trying to do is take the input of a path from the user and recursively create the directories as I go.

How do I convert the value from $k to its actual value and pass it as a parameter ?
# 2  
Old 11-22-2014
As i see it, not really understanding awk yet, but you're comparing a STRING (a) with an INTEGER (k).
Anyhow, so you pass a list of variables, and when it matches a certain string, you want to call that function?

Must it be awk, because bash works just fine Smilie
Code:
#!/bin/bash
my_func_local() {
    echo "In func: my_func_local $1"
}

for ARG in "${@}";do
    [[ $ARG = a ]] && \
        my_func_local $ARG || \
        echo $ARG
done

Code:
sh script.sh a b c d
In func: my_func_local a
b
c
d

Hope this helps
# 3  
Old 11-22-2014
What you are getting surprises me when I look into the script you post:
If you'd define the function you call correctly, this might work better (my_func_local vs. my_local_func). And, don't put $k into the quotes to have it evaluated for the system call. And, awk uses sh to run the system call. Having symlinked /bin/sh to /bin/bash, I get
Code:
In func a
b
c
d
e

# 4  
Old 11-22-2014
The answer is simple: awk is not shell. Variables don't work that way. $ means column here, and isn't even expanded inside quotes.

Code:
system("my_local_func " k)

# 5  
Old 11-22-2014
Quote:
Originally Posted by RudiC
What you are getting surprises me when I look into the script you post:
If you'd define the function you call correctly, this might work better (my_func_local vs. my_local_func). And, don't put $k into the quotes to have it evaluated for the system call. And, awk uses sh to run the system call. Having symlinked /bin/sh to /bin/bash, I get
Code:
In func a
b
c
d
e

Can you please specify in details what you have done to get the result ? can you post your entire script which shows the symlink ?

---------- Post updated at 11:26 PM ---------- Previous update was at 11:18 PM ----------

Quote:
Originally Posted by Corona688
The answer is simple: awk is not shell. Variables don't work that way. $ means column here, and isn't even expanded inside quotes.

Code:
system("my_local_func " k)

What you have told me to do doesn't work. I am using utilizing the following code now-:
Code:
function my_local_function {
echo $1
}

export -f my_local_function

echo $1 | awk -F"/" '{ for (k=1;k<=NF;k++)
{
if ( $k == "a" ) {
    system("my_local_function" k)
        }
else {
    print $k
    }
    }
}'

I am getting the following erroneous error-:
Code:
sh: my_local_function1: command not found
b
c
d

---------- Post updated at 11:30 PM ---------- Previous update was at 11:26 PM ----------

Quote:
Originally Posted by sea
As i see it, not really understanding awk yet, but you're comparing a STRING (a) with an INTEGER (k).
Anyhow, so you pass a list of variables, and when it matches a certain string, you want to call that function?

Must it be awk, because bash works just fine Smilie
Code:
#!/bin/bash
my_func_local() {
    echo "In func: my_func_local $1"
}

for ARG in "${@}";do
    [[ $ARG = a ]] && \
        my_func_local $ARG || \
        echo $ARG
done

Code:
sh script.sh a b c d
In func: my_func_local a
b
c
d

Hope this helps
Can you please explain to me what your script means step by step ? Sorry for being blunt but I am comfortable with awk rather than raw shell scripting. However for this problem it does not matter what I use so if you can explain how your script works then it would be fine for my purpose.
# 6  
Old 11-22-2014
As requested:
Code:
sudo ln -sf /bin/bash /bin/sh
echo "a/b/c/d/e" |
awk -F"/"       '{for (k=1;k<=NF;k++)   {if ($k == "a" )        {system("my_func_local " $k)}
                                         else                   {print $k}
                                        }
                 }
                '
In func a
b
c
d
e

Don't forget to recreate the original sh symlink.

Last edited by RudiC; 11-23-2014 at 09:31 AM.. Reason: typo
This User Gave Thanks to RudiC For This Post:
# 7  
Old 11-22-2014
Quote:
Originally Posted by RudiC
As required:
Code:
sudo ln -sf /bin/bash /bin/sh
echo "a/b/c/d/e" |
awk -F"/"       '{for (k=1;k<=NF;k++)   {if ($k == "a" )        {system("my_func_local " $k)}
                                         else                   {print $k}
                                        }
                 }
                '
In func a
b
c
d
e

Don't forget to recreate the original sh symlink.
Thanks. But can you tell me why did you need to create a symlink /bin/sh for this to work ? I mean whats the logic behind this. Why wasn't it working before ?
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