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DOC: configuration: add clarification on escaping in keyword arguments

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Add a more precise description on how backslash escaping is different
than the top-level parser, and give examples of how to handle single
quotes inside arguments.
This commit is contained in:
Thayne McCombs 2021-10-04 01:02:58 -06:00 committed by Willy Tarreau
parent aa992761d8
commit cd34ad7133
1 changed files with 11 additions and 3 deletions
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14
doc/configuration.txt
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@ -613,7 +613,7 @@ if a closing parenthesis is needed inside, this one will require to have its
own quotes.
The keyword argument parser is exactly the same as the top-level one regarding
quotes, except that is will not make special cases of backslashes. But what is
quotes, except that the \#, \$, and \xNN escapes are not processed. But what is
not always obvious is that the delimiters used inside must first be escaped or
quoted so that they are not resolved at the top level.
@ -692,14 +692,22 @@ thus single quotes are preferred (or double escaping). Example:
arg3 ______________________/
Remember that backslashes are not escape characters within single quotes and
that the whole word3 above is already protected against them using the single
that the whole word above is already protected against them using the single
quotes. Conversely, if double quotes had been used around the whole expression,
single the dollar character and the backslashes would have been resolved at top
level, breaking the argument contents at the second level.
Unfortunately, since single quotes can't be escaped inside of strong quoting,
if you need to include single quotes in your argument, you will need to escape
or quote them twice. There are a few ways to do this:
http-request set-var(txn.foo) str("\\'foo\\'")
http-request set-var(txn.foo) str(\"\'foo\'\")
http-request set-var(txn.foo) str(\\\'foo\\\')
When in doubt, simply do not use quotes anywhere, and start to place single or
double quotes around arguments that require a comma or a closing parenthesis,
and think about escaping these quotes using a backslash of the string contains
and think about escaping these quotes using a backslash if the string contains
a dollar or a backslash. Again, this is pretty similar to what is used under
a Bourne shell when double-escaping a command passed to "eval". For API writers
the best is probably to place escaped quotes around each and every argument,