editing standard input file in shell script

Question

I got a problem to read standard input file, to edit the standard input, and to write the output to other file. So, the shell will be run with command like this:

./shellName < inputFile > outputFile

so I write my shell like this:

read INPUT
tr '[:upper:]' '[:lower:]' INPUT
grep "<td>" INPUT | sed -r 's/<td>([^<]*)<\/td>/\1/g' #to search all line that contain <td> and delete <td> and <\/td>
echo $INPUT

then, I just realize that the command read is read the standard input line by line. the code itself didn't work. I tried to change all uppercase to lowercase, and then delete and </td> on line that contain . What should I do? if I require to create an temp file, how can I create an temporary file in the shell?

DrC · Accepted Answer · 2013-01-18 22:13:25Z

1

It is actually much easier than you think. By default, tr reads from stdin (fd 0). The commands inside your script "inherit" stdin from the script unless you redirect it. So something like

#!/bin/sh
tr '[:upper:]' '[:lower:]' | sed -E 's/<td>([^<]*)<\/td>/\1/g'

I changed -r to -E as that is needed on my platform.

answered Jan 18, 2013 at 22:13

DrC

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2 Comments

user1988385 Over a year ago

wow. thx man. it works! btw what is -E? cant find it on the man page

DrC Over a year ago

On OS X it is the option to use extended regular expressions. The equivalent to the -r you used on linux (I just checked my linux box).

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