[rrd-users] problem with 'cat file | rrdtool - ' syntax

Kiss Gabor (Bitman) kissg at ssg.ki.iif.hu
Tue Jan 15 15:13:13 CET 2013

> I have a little problem to change rrdtool graphing mode from normal to pipe:
> For example my test file contains:
> rrdtool graph lpar.png --imgformat PNG \
> --title "test" \
> --width 800 --height=400 \

> and if I lauch this simple script, no problem, I get graph
> Now how to generate same graph, but with a pipe syntax, like 'cat file |
> rrdtool - ' or 'rrdtool - < file' ?
> I have tried to just remove 'rrdtool' from the file listed upper, and then
> perform a cat file | rrdtool - , and the result is:
> ERROR: Could not make sense out of '\'

This is not rrdtool problem but a shell issue. :-)
It is the shell who joins continuation lines preceded by backslash+newline.

       A non-quoted backslash (\) is the escape character.  It  preserves  the
       literal value of the next character that follows, with the exception of
       <newline>.  If a \<newline> pair appears,  and  the  backslash  is  not
       itself  quoted,  the \<newline> is treated as a line continuation (that
       is, it is removed from the input stream and effectively ignored).

Command rrdtool receives its arguments as if they were
written in a single line.


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