UNIX for Dummies Questions & Answers

Hi,

I have a problem with retreiving the value of an environment variable. The name of the variable is:

DIR$INP

I am not able to change the name of the variable, because it is used by programs to which I do not have access to. The variable contains the name of a directory as value. I have tried many things to access this value on a shell, but I haven't succeeded. I've tried things like:

echo $DIR$INP

echo $DIR\$INP

echo ${DIR\$INP}

echo $'DIR\$INP'

echo $"DIR\$INP"

Nothing seems to work. Can anybody help me please... Thank you,

kind regards,
Lamac

What shell are you using that allows a '$' in a variable name? How does it get set? This looks like a VMS-ism to me --- are you running some program cross platform?

Is this a homework question?

I'm using SunSolaris.

I know, it sounds crazy, it's not my fault. I'm migrating a VAX/VMS (no I'm not 60 years old...) application to UNIX, but I'm not that much aquainted with UNIX. But I do know how to read values from a shell.

The value is set with "setenv", like this:

setenv 'DIR$INP' "$HOME/cart/log"

This works, and I can see the values in the environment. But I can't access the value with $DIR\$INP. I don't get it.

Okay, you're using csh or tcsh: Both will allow you to set such a variable, but neither will allow you to use it in the shell. If you need the value of this variable at the shell level do something like one of these:

Code:

setenv 'DIR$INP' "$HOME/cart/log"
awk 'BEGIN { print ENVIRON["DIR$INP"] ; exit }'
# a less direct alternative:
env | grep '^DIR$INP' | cut -d= -f2
# or equivalently:
env | awk -F= '/^DIR$INP/ { print $2 }'

At least one of these should work.

Yea,

thanks, the second one works. But what does it do? If it's not too much trouble, couöd you just briefly explain??

Thanks,
Mitch

Okay, assuming you mean this one:

Code:

env | grep '^DIR$INP' | cut -d= -f2

"env" just echoes the entire environment to standard output.

"|" strings the standard output of one command to the standard input of the next; this is called a "pipe" or (as a transitive verb) "piping".

grep (global regular expression print) selects lines from its input according to a specification. Putting the specification in apostrophes prevents expansion of shell variables. Consult the man page for more --- much more!

The result of grep is the piped into "cut". "-d=" tells cut to separate fields by the equal sign, and "-f2" tells it to print the second field.

This solution should probably be changed to

Code:

env | grep '^DIR$INP=' | cut -d= -f2

to prevent the grep from matching on DIR$INPUT_SEQUENCE, DIR$INPUT_METHOD, etc.

NB: I'm surprised that the awk in Solaris doesn't take the first solution ... maybe change "awk" to "nawk"? Consult the man pages to find out why.

OK, I really got it. Thanks a lot. Great help.

GreetX,
Mitch