Re: [opensuse] bash - why doesn't the tldp bash beginners guide for loop example work?
- From: David Bolt <bcrafhfr@xxxxxxxxxx>
- Date: Thu, 14 Feb 2008 14:56:45 +0000
On Wed, 13 Feb 2008, David C. Rankin wrote:-
Listmates,
I have run into a bash problem with a simple for loop I don't
understand and would like input from the gurus to determine if the tldp
documentation is in error or if it is me. Safe money says it's me, but
here is the situation.
I'll give you three guesses which one...
I am using example 9.1.2.2. from the following link to construct
a simple for loop to extract a directory full of zip files:
http://tldp.org/LDP/Bash-Beginners-Guide/html/sect_09_01.html
The example give is:
[carol@octarine ~/html] cat html2php.sh
#!/bin/bash
# specific conversion script for my html files to php
LIST="$(ls *.html)"
for i in "$LIST"; do
NEWNAME=$(ls "$i" | sed -e 's/html/php/')
cat beginfile > "$NEWNAME"
cat "$i" | sed -e '1,25d' | tac | sed -e '1,21d'| tac >> "$NEWNAME"
cat endfile >> "$NEWNAME"
done
Oh, oh. There's an error in that. As you guessed, the quotes around
"$LIST" shouldn't be there. Using some HTML files in one of my
directories as an example:
davjam@adder:~/public_html> ls *.htm
index.htm pics1.htm spam3days.htm spams7day.htm spamstats.htm
pic.htm rsync.example.htm spams3day.htm spams_per_day.htm you.htm
That shows the files, just for reference.
davjam@adder:~/public_html> LIST="$(ls *.htm)"
That's the first line in that script.
davjam@adder:~/public_html> echo "${LIST}"
index.htm
pic.htm
pics1.htm
rsync.example.htm
spam3days.htm
spams3day.htm
spams7day.htm
spams_per_day.htm
spamstats.htm
you.htm
And there was the contents of $LIST.
davjam@adder:~/public_html> for i in "${LIST}"; do echo "\"${i}\""; done
"index.htm
pic.htm
pics1.htm
rsync.example.htm
spam3days.htm
spams3day.htm
spams7day.htm
spams_per_day.htm
spamstats.htm
you.htm"
Now, here I've passed "$LIST" to the for loop and the body just prints
the contents of $i and adds quotes around it so you can see just what is
passed as $i. As you can see, there is a double-quote at the beginning
of the first line, and the closing quotes at the end of the last line.
This says that everything in between those quotes was assigned to $i in
one go.
As you correctly guessed, the quotes around $LIST shouldn't have been
there, and removing them gets this output instead:
davjam@adder:~/public_html> for i in ${LIST}; do echo "\"${i}\""; done
"index.htm"
"pic.htm"
"pics1.htm"
"rsync.example.htm"
"spam3days.htm"
"spams3day.htm"
"spams7day.htm"
"spams_per_day.htm"
"spamstats.htm"
"you.htm"
<Snip>
I understand enough to realize the quotes affect bash expansion,
but I am curious as to whether the tldp example is in error. What says
the brain trust?
Yes, there's an error in the tldp example.
Regards,
David Bolt
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- From: David C. Rankin
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