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Passing variables to a sed function

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# 1  
Old 07-09-2014
Passing variables to a sed function
Hi everyone,
I've re-written some of our scripts to use more functions and I've run into a situation where passing a variable to a sed function does not work. My function is a one-liner sed command as follows:

Code:
function StringSub()
{
sed -i "${1}/${2}/${3}/${4}" ${5}
}

Where ${1} through ${4} represent command/ pattern/ replacement/ flag/ respectively. ${5} is used to pass the filename.
It may seem like overkill but I am hoping I can take the five parameters from a .csv file to pass to the function, down the road once this is developed more.

Code:
echo "Enter the two-digit month, and the four-digit year for the report, then press enter."
read tidyMonth tidyYear
#use the values to create a date column, always set to the first of the month.
awk -v column=1 -v value="${tidyMonth}/01/${tidyYear}" '
BEGIN {
FS = OFS = ",";
}
{
for (i=NF +1; i > column; i-- ) {
$i = $(i-1);
}
$i = value;
print $0;
}
' originalSource.csv > mysource.csv
#Next, rename first row, first field to 'Date'
StringSub '1s' '${tidyMonth}\/01\/${tidyYear}' 'Date' 'g' 'mysource.csv'
StringSub '1s' 'Video' 'Product+Video' '' 'dateColumnAdded-02.csv'

The file mysource.csv takes the form:
Code:
06/01/2014,Video,Views
06/01/2014,video_title_1,34
06/01/2014,video_title_6,12
06/01/2014,video_title_3,102

Basically the StringSub function works, until I have a variable to pass that I suspect has slashes in it. Is it something I'm doing wrong in my expansion, or lack thereof? The second call of StringSub which renames 'Video' to 'Product+Video' works without any issue.
This is what I end up with:
Code:
06/01/2014,Product+Video,Views
06/01/2014,video_title_1,34
06/01/2014,video_title_6,12
06/01/2014,video_title_3,102

Last edited by Corona688; 07-09-2014 at 02:06 PM.. Reason: Use [code], not [icode] please
# 2  
Old 07-09-2014
Variables are substituted in "double quotes" only:
Code:
StringSub '1s' "${tidyMonth}\/01\/${tidyYear}" 'Date' 'g' 'mysource.csv'

This User Gave Thanks to MadeInGermany For This Post:
richardsantink
# 3  
Old 07-09-2014
Overkill is an incredible understatement... Each time you run sed you're reading, editing, and replacing the entire file. All for a single operation.

Why not just do everything in awk at the same time you're doing the other operations? You can do similar sorts of operations, but without having to run sed 12 times.
# 4  
Old 07-10-2014
Quote:
Originally Posted by Corona688
Overkill is an incredible understatement... Each time you run sed you're reading, editing, and replacing the entire file. All for a single operation.

Why not just do everything in awk at the same time you're doing the other operations? You can do similar sorts of operations, but without having to run sed 12 times.
Thankfully at this stage, it's still easy to manage. Down the road as I gain skill I hope to clean up my code a bit!!

Thanks for the reply,

R
# 5  
Old 07-10-2014
Let me put it this way... if you applied all the effort spent learning sed to awk, you could do this. It's a lot simpler in some ways, being a languge with if and else and then and code blocks and variables, instead of a state machine with jumps and conditions and buffers.
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