Bash foreach loop | 易学教程

问题

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.

回答1:

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

回答2:

"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/

回答3:

Here is a while loop:

while read filename
do
    echo "Printing: $filename"
    cat "$filename"
done < filenames.txt

回答4:

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 %"

回答5:

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> _

回答6:

cat `cat filenames.txt`

will do the trick

回答7:

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)

来源：https://stackoverflow.com/questions/4162821/bash-foreach-loop

标签

bash

foreach