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RE: Recommended way to truncate a shell variable value in autoconf
From: |
Dale Visser |
Subject: |
RE: Recommended way to truncate a shell variable value in autoconf |
Date: |
Fri, 21 Feb 2014 22:37:57 -0500 |
David:
I looked at the docs and see what you mean. Amazing how portability concerns
affect even the lowly echo command. I will try replacing
echo "$X"
with
AS_ECHO([$X]).
Thank you!
Dale
Sent from my Windows Phone
________________________________
From: David A. Wheeler<mailto:address@hidden>
Sent: 2/21/2014 9:55 PM
To: autoconf<mailto:address@hidden>
Subject: RE: Recommended way to truncate a shell variable value in autoconf
Eric Blake said:
> .... Just go with:
> X=`echo "$X" | sed 's/[, ].*//'`
The "sed" is nice and clear.
However, that "echo" will probably cause trouble if $X starts with "-" or has
other characters in it.
I presume in this case that $X will *usually* start with "-", so you REALLY
don't want to use echo directly.
Unless $X can *only* contain alphanumerics, I suggest replacing echo "$X" with:
printf '%s\n' "$X"
An alternative would be to use AS_ECHO.
Dale Visser, you might want to look here:
https://www.gnu.org/savannah-checkouts/gnu/autoconf/manual/autoconf-2.69/html_node/Portable-Shell.html
and especially:
https://www.gnu.org/savannah-checkouts/gnu/autoconf/manual/autoconf-2.69/html_node/Limitations-of-Builtins.html
--- David A. Wheeler
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