bash scripting

playonmonkey · 02-15-2012, 07:15 PM

#!/bin/bash
VAR1=file name
echo "Enter a File name and press Enter:"
read VAR1
echo "file created: $VAR1"
touch $VAR1

root@ubuntu:~# ./lab7parta.sh
./lab7parta.sh: line 2: name: command not found

Enter a File name and press Enter:
joe
You typed: joe
./lab7parta.sh: line 6: var1: command not found

how do i fix this

sundialsvcs · 02-15-2012, 07:31 PM

If you choose to monkey-around with "good ol' bash"

... then you will for the time being have to content yourself with Bash's somewhat-extremely-limited viewpoint with regard to the entire world.

your choice ...

Bash doesn't understand "VAR1=file name" ...

... because Bash thinks a whole lot more about blank spaces ...

... than it does about newline (\n).

You see, Bash looks at your string as consisting of the following fifteen ASCII characters: VAR1=file(blank_space)name(newline)

"That's it. That's all."

"It's just a computer program, after all, therefore it goes without saying that it is rather incredibly simple."

Quote:

And, to be completely fair, it was written by Brian Fox in 1989 (why, it was only yesterday... seriously!) "as a replacement for the Bourne shell." (I do hereby beg your indulgent indulgence, Brian, and I trust that you know I am not hereby besmirching you, my esteemed colleague ...)

... To fully understand the sometimes bizarre error messages that a computer program now produces, you do need to appreciate its designers' perspective at the time.

(At the time, trust me on this,

they made perfect sense. Meanwhile, "deal with it.")

playonmonkey · 02-15-2012, 07:34 PM

trust me I dont choose this I have to do it for school and have been messing with it all day and just cant get it if i could what the file should like then i would be able to figure out what i did wrong

catkin · 02-16-2012, 01:10 AM

When you want to assign a value including a space to a variable, you need to put it in single quotes: foo='value with spaces'

That's not the whole story but it will do for starters.

EDIT: and when you want to use a variable which contains spaces, and keep those spaces as spaces within the value, you need to put it in double quotes: touch "$foo"

uhelp · 02-17-2012, 10:15 AM

Code:

#!/bin/bash

# don't do this
#VAR1=file name
#echo "Enter a File name and press Enter:"
#read VAR1
#echo "file created: $VAR1"
#touch $VAR1

read -p 'Enter 3 file names on a line separted by blanks,  please : '  file1 file2 file3

echo $file1
echo $file2
echo $file3

read "help read"
"help internalCommand" gives help on bash internalCommand.
"read" is a builtin.

For sure it will throw errors in the second line, as this line is interpreted as:
assign VAR=file
execute command "name"

if you want to assign a string containing blanks use:
var=' This is a string with some blanks in it assigned to var.'
echo $var

and: DO NOT USE CAPS for vars.
The environment vars are by convention all in caps.
Using var names ThisIsMyVar will prevent from accidentally changing a environment var.
This is much better style and much more safe!

And some remarks to bash scripting in general:
bash is a shell.
It is NOT a fully featured programming language.
It's primary goal is, to give you a reliable interface to the system.
So that you can easily start commands, deal with the ProcessManagment and so on.
And therefore has to follow the general *nix philosophy.

Blaming it therefore is a kind of shortsighted view.
It is a great programm with lots of astounding features,
to the price of strange syntax.
Keep on learning it.
The reward is very high.