I have an input (let's say a file). On each line there is a file name. How can I read this file and display the content for each one.
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7 Answers
Something like this would do:
xargs cat <filenames.txt
The xargs program reads its standard input, and for each line of input runs the cat program with the input lines as argument(s).
If you really want to do this in a loop, you can:
for fn in `cat filenames.txt`; do
echo "the next file is $fn"
cat $fn
done
3 Comments
mivk
Both of these don't work when the filenames contain spaces.
Toochka
@mivk you can escape the space
kernelize
To allow spaces in filenames, IFS can be set to newline only before the for loop and unset after the loop to restore the default behaviour (using
IFS=$'\n' and unset IFS)"foreach" is not the name for bash. It is simply "for". You can do things in one line only like:
for fn in `cat filenames.txt`; do cat "$fn"; done
Reference: http://www.cyberciti.biz/faq/linux-unix-bash-for-loop-one-line-command/
Comments
Here is a while loop:
while read filename
do
echo "Printing: $filename"
cat "$filename"
done < filenames.txt
If they all have the same extension (for example .jpg), you can use this:
for picture in *.jpg ; do
echo "the next file is $picture"
done
(This solution also works if the filename has spaces)
1 Comment
Tom Russell
I think there are situations in which it is useful to surround
*.jpg with quotes, IIRC: for picture in "*.jpg";...xargs --arg-file inputfile cat
This will output the filename followed by the file's contents:
xargs --arg-file inputfile -I % sh -c "echo %; cat %"
answered Nov 12, 2010 at 10:41
Dennis Williamson
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Comments
You'll probably want to handle spaces in your file names, abhorrent though they are :-)
So I would opt initially for something like:
pax> cat qq.in
normalfile.txt
file with spaces.doc
pax> sed 's/ /\\ /g' qq.in | xargs -n 1 cat
<<contents of 'normalfile.txt'>>
<<contents of 'file with spaces.doc'>>
pax> _
Comments
cat `cat filenames.txt`
will do the trick
