topic Re: While Read a File in Operating System - Linux

While Read a File

Bob Ferro — Wed, 28 Nov 2007 14:27:35 GMT

I have a simple one. I have a script with the following lines:

cat email_list | while read L
do
mailx -s "Test Data" $L < /dev/null
done

The email_list is a file with various email address, one line per email address. Let's say I have 10 entries and I want to comment out one line with an "#". Now when my script runs, I want to send an email out to 9 people instead of 10. I want to comment out the address rather than delete it. How can I set up my "while read" instruction to bypass any lines with an "#" in it?

Re: While Read a File

Pete Randall — Wed, 28 Nov 2007 14:46:06 GMT

Bob,

For my simple mind, the following works:

for L in `cat email_list |grep -v '#'`
do
mailx -s "Test Data" $L < /dev/null
done

Pete

Re: While Read a File

Bob Ferro — Wed, 28 Nov 2007 15:00:14 GMT

Bam!

Pete, it worked like a charm. Thanks again.

Re: While Read a File

James R. Ferguson — Wed, 28 Nov 2007 15:01:55 GMT

Hi Bob:

One simple way:

# cat ./mailer
#!/usr/bin/sh
while read X L
do
[ ${X} = "#" ] && continue
mailx -s "Test Data" ${L} < /dev/null

done < email_list

If your file has a "#" field as the first field of the line it will be skipped.

Notice, too that your can eliminate the 'cat' process. The loop reads your file directly.

Regards!

...JRF...

Re: While Read a File

blah2blah — Wed, 28 Nov 2007 17:36:51 GMT

i cant beleive you guys missed the details.

Pete, you know the # should be at the begining of the line and therefore your grep should be anchored to the begining of the line: grep -v "^\#"

and James, your solutions assumes there is always a space after the #, as in:
# thisworks
#thisdoesn't

and you improve performance by eliminating the cat, but still run mailx for each address

something like this would be better,
comments can be at the end of the line,
as in:
addr # to me

will work and it creates a variable of the addresses and runs mailx just once

addrs=""
while read myAddr
do
myAddr=${myAddr%%#.*} #remove first # and everything on the line after it
myAddr=${myAddr%%#} #remove # if it is last character on the line or only character
addrs="${addrs} ${myAddr}"
done < email_list

mailx -s sub $addrs