How does one execute a command (like sed) in a bash script and
have the result (what that command would have printed to stdout)
be assigned to a script variable. For exampe (this does not work,
but perhaps my intent can be guessed by it)

#!/bin/bash

f=sed 's/\(.*\.ps\)\(\.gz\)*/\1/' $1
if [ $1 = $f ] ; then
echo $1
else
echo $f
fi

I want the result of sed to be the value of the variable f,
next I want to compare the value of f with the value of the
first argument to the script. If the result of the comparison
is true (meaning the strings are the same) then I want to
print out the value of the first argument to the script; otherwise
I want to print the value of the variable f.

Put the command in backticks, like so:
f=`sed 's/\(.*\.ps\)\(\.gz\)*/\1/' $1`

Ok., but i evidently have a problem with sed.

I understand now that my example should have contained something like

f=`echo $1 | sed 's/\(.*\.ps\)\(\.gz\)*/\1/'`

but this does not accomplish my intent as far as sed goes. I want sed to
look for the pattern something.ps.gz and change it into something.ps
(i.e., remove the trailing .gz). How is that done with sed?

Hi,

The trick is to use backquotes i.e `, upper left of your keyboard, beneath the tilde. So I guess you want something like

#!/bin/sh

f = `echo $1 | sed -e 's/\.ps/\.gz/'`
echo $f


Groetjes,

Kees-Jan

Ok, ok, I am catching on... My problem is with paths, not with sed.
My script is now in final form:

#!/bin/bash

f=`echo $1 | sed 's/\(.*\.ps\)\.gz/\1/'`
if [[ $1 = $f ]] ; then
/usr/bin/ghostview $f
else
gunzip $1
/usr/bin/ghostview $f
fi

And it works if in a Konsole I type the complete path to the name of the
script ( /home/dpaddy/bin/ghostview ). It does not work if I just type
something like ghostview b.ps.gz and leave the complete path to
my ghostview script out. My PATH environment variable is

PATH=/home/dpaddy/bin:/usr/kde/3.2/bin:/bin:/usr/bin:/usr/maple9.5/bin:/usr/local/bin:/opt/bin:/usr/i386-pc-linux-gnu/gcc-bin/3.3:/usr/X11R6/bin:/opt/blackdown-jdk-1.4.1/bin:/opt/blackdown-jdk-1.4.1/jre/bin:/usr/qt/3/bin:/usr/kde/3.2/bin

so I would have thought that my script would be what the system
would execute given the command ghostview. Is this like windows...
do I need to reboot since I am making a change? How do I get
my script to be invoked without typing the complete path?

Oooops
Sorry,

I'm kind of new to this website. Didn't read the replies yet.

But what you want is probably:
f=`echo $1 | sed -e 's/\.ps\.gz$/\.ps/'`

to take gz of a ps file, or

f=`echo $1 | sed -e 's/\.gz$//'`

to take gz of any file.

In this last case, you could also do
f=`basename $1 .gz`

Sorry again,

Groetjes,

Kees-Jan

Catching up as well....

You can modify your path at any time by typing
export PATH=/your/new/path

after that, your new path will be used in the current console only.

Alternatively, you can edit your ~/.profile or ~/.bashrc or something, and change the path there. In that case, you will need to log out and back in for the changes to activate.

At any time, you can type "echo $PATH" to view your current path, or "which ghostview", to find out which ghostview will be used.

Having said all that, it's probably not a good idea to have two commands on your system with the same name. It is bound to cause confusion (as you are already experiencing). I suggest you rename your script to something else (i.e. mygv or something)

Groetjes,

Kees-Jan