tech-pkg archive

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Old Index]

Re: SUBST_SED and newline?

Georg Schwarz schrieb:

Am 09.12.2009 um 23:43 schrieb fulvio ciriaco:

I guess it involves SUBST_SED being invoked inside a higher
substitution level and that one needs to escape one level more,

probably. However, I think in that case any multiple escaping tricks should be avoided because they could easily break on any slight change of the buildlink infrastructure.

I don't think so. Once the developer understands which escaping is necessary at exactly which place, it isn't that complicated anymore, and this behavior is even supported by POSIX. So let's start: We want to have a sed command that surrounds each line "#include <sys/io.h>" with an #if...#endif block. The basic syntax for this is:

s,^#include <sys/io\.h>,#ifndef __sun\
#include <sys/io.h>\

The backslashes at the line ends are required by sed, as explained in the POSIX manpage.

Now let's convert this string into a valid bmake string, for use in a variable assignment. This means that every # has to be escaped as \#, and the newline has to be written as ${.newline}. Nothing more:

SUBST_SED.sysio+= -e 's,^\#include <sys/io\.h>,\#ifndef __sun\${.newline}\#include <sys/io.h>\${.newline}\#endif,'

(the above is meant to be a single line of code.)

The difference to Georg's suggestion is the single backslash, not the double backslash before the ${.newline}. Like that, it works fine for me here on Interix, and probably everywhere else.

The double backslashes don't work because sed still sees them as double backslashes, so it interprets the ${.newline} that follows immediately as a real newline and not as an escaped one.

(Maybe I should teach pkglint to analyze this kind of problems the same was as I just did. Or would that be overkill? ;))


Home | Main Index | Thread Index | Old Index