UNIX question

The Bollox

I am currently studying for my repeats and I came across a problem.

the first part was easy enough. take in a variable from the command line and check it was ok.

but in the second part it asks me to input a series of variables from the command line.

I know I need to use a loop (while loop is probably the best) but I can't get the coding right in my head. some help would be appreciated.

I was going along the lines of:

while [ $i -ne *something* ]
do
-code

I don't know how to say 'until the $i string is empty'

AARRRGH

It would probably help if you told us what language you are programming in.

The Bollox

I dunno what it is, just the unix standard, I didn't think it had a name other than unix

well Unix shell programming if that makes it any clearer

AARRRGH

Unix is an Operating System, not a programming language

Do any of these ring a bell?

Perl
Bash
Tcl
...?

The Bollox

unfortunatly no, shows what we learn in college, eh? :rolleyes:

it's the this particular one uses the Korn shell

is there much of a difference between them?

Creamy Goodness

you can use the wild card # which counts the amount of command line arguments and stores it in a variable.

eg ./shellscript.sh 5 6 7 8 ----> $# will contain 4.

The Bollox

ah right, cheers. unfortunaly I don't have access to UNIX at home so I can't play around with it

Creamy Goodness

you can download an UNIX operating system (eg. ubuntu) and use the terminal program in that or download cynwin (emulates a UNIX environment in windows.)

or if you had a ssh shell in college you could log into that using putty.

The Bollox

I use the one in college when I'm there. we have both RedHat and can access a remote desktop thing through Telnet.

I will deffinitly be getting my hands on Ubuntu once I get myself a laptop. one of the lads in work has it, it's savage. miles ahead of other OS's

AARRRGH

Can I ask, is it the syntax you are having problems with or the general concept of looping?

daymobrew

The Bollox wrote:

while [ $i -ne *something* ]
do
-code

I don't know how to say 'until the $i string is empty'

$ man test
....
       -n STRING
              the length of STRING is nonzero

       -z STRING
              the length of STRING is zero
....

So you could either test that the string has something or is empty. Put quotes around the variable.

while [ -n "$i" ]
do
  echo $i
done

IRLConor

#!/bin/sh

for arg in "$@"; do
    echo $arg
done

does:

> sh test.sh foo bar 'foo bar' "foo bar"
foo
bar
foo bar
foo bar

The Bollox

dublindude wrote:

Can I ask, is it the syntax you are having problems with or the general concept of looping?

I know the general idea behind looping. I can perform it in Java and C#, it's just the syntax. like in Java you say

i = 10
for (x = 1; x < i; x++)
{
blah blah
x++
}

I just wanted to know if there was a similar way of doing it in this language

IRLConor

FYI, the language is "sh". On Linux sh is usually just an alias for bash (which is kind of an extended more fully-featured copy of sh). On other UNIX or UNIX-like operating systems sh may not be bash and bash may not exist.

Type man sh or man bash in a Linux/UNIX terminal or in a Google search box for the language documentation.

The Bollox

cool, cheers

Tom Dunne

echo $SHELL might be a start, at least you will know what shell you are using.