UNIX for Dummies Questions & Answers

Do Tab or Enter behave like a command in some cases? For example,
I had been trying to plot with gnuplot by usinf shell script like command inside:

cat plot.gnu gives :
plot 'datafile1' , \
'datafile2'

Now gnuplot doesn't recognize the newline command "\"
unless I use "enter" in the vi-editor.
i.e. gnuplot -persist plot.gnu doesn't work

Similarly I found that commands are not recognized in Makefile if I don't specifically use "tab" space inside the vi-editor.
(I could have made a tab-space by using 'echo' in a shell script file, but that doesn't work!)

Thank you in advance.

"\" isn't a newline but something that commonly escape the next character, precisely a newline in your example.
That's by design, a tab must precede commands in the Makefile syntax.
Just use instead:

Code:

printf "\t"

Dear Jiliagre,

Thanks for the reply. I'll try this for tab. But what about the making newline instruction? What could be the way to resolve the problem in my first example?

Please explain better the problem you have with your first example with error messages if any. Newline is anyway unlikely an instruction per itself but probably a command separator.

Thanks. Let me try once again. My example may be specific to gnuplot. But it may arise to other cases.

If run the follwing commands :

Code:

#!/bin/bash
echo "plot  \ " > temp
for f in 2 3
do
echo "x**"$f", \ " >> temp
done
echo "x**4" >> temp
cat temp | gnuplot -persist
rm -f temp

=======

I find the following error messages :

Code:

gnuplot> plot  \ 
               ^
         line 0: invalid character \


gnuplot> x**2, \ 
               ^
         line 0: invalid character \


gnuplot> x**3, \ 
               ^
         line 0: invalid character \


gnuplot> x**4
         ^
         line 0: invalid command

====================

Whereas

Code:

echo "p x**2, x**3, x**4"|gnuplot -persist

works successfully though it's the same in principle.


Hope I could clarify this time. My observation is that the newline separator (" \") is not recognized by the shell always.

I have attached the shell script as well. You may need to install gnuplot in case it's not installed by your distribution.

Thanks and best regards.

\ at the end of the line is the only case where \ does not work as an escape character. Rather, it removes the linefeed character that follows altogether..

@Scrutinizer

Sorry, did you mean " \" skips all the lines after it or the next line only?