Shell Programming and Scripting

Hi everybody!

I am writing a script which accepts two arguments one of them being a message. All is working except for the message part. That is, to accept text as an argument.

I have trouble storing and echoing a line of text. It seems that writing a few words and store them in an argument ($1) does not work right off the hat, as it is it, prints only the first word I write because if what I write has spaces then it encounters the null character and the script terminates. EXAMPLE:

If I write : “hi how are you?” It will only print the word “hi”.

Code:

  #!/bin/sh
  echo $1>>file.txt
  text=`tail -5 file.txt`
  echo "$text">file.txt

What I have done to overcome this problem is to echo subsequent arguments like this:

Code:

 echo the message is  '"'$1 $2 $3 $4 $5 $6 $7 $8 $9'"'

But I don`t like it and it is not what I want. I want a full line including “\0” and all! I have looked at grep and cat but I have been unsuccessful at finding a solution. Can somebody point me in the right direction?


Bluetxxth

Compare these two runs:

Code:

./yourscript.sh Hello World, how are you?
./yourscript.sh "Hello World, how are you?"

HI Pludi thank you much for your answer.... !!!

It works !!! Shall I assume that I just have to put the citation marks and that that was all that happened?

Regards,

bluetxxth

Yes. The shell splits the command line based on whitespace characters (space, tab, ...), and thus treats all tokens ("words") as separate arguments. When using quotes (either double or single), that special meaning is removed, and the whitespaces are used as part of the argument.

I see... however, it just occurs to me ... if the double quotes cannot be "induced " for example something like when one writes with back quotes to expand what is inside them.

Code:

 `cat file.txt`

Not when reading, but when printing the contents again. Assume you have a file "file.txt" with the following contents:

Code:

This  is a test	with   variable		whitespaces

It contains single and multiple spaces, and tabs just for fun. Now let's read it:

Code:

#!/bin/bash
line=$( cat file.txt ) # $() is the advanced version of backticks
echo $line
echo "$line"

See the difference? In the first output, echo takes all the arguments (more than one, as the shell split on the whitespaces), and outputs them with the default concatenation character (first character in $IFS, by default a single space). The second line, however, passes the string as it is to echo, as a single argument, and all the special characters in it are preserved.

Oh okay.... I see the point.... Thnx so much!!!

BR,

Blue