|author||Rob Pike <firstname.lastname@example.org>||Tue Mar 10 15:08:55 2015 -0700|
|committer||Rob Pike <email@example.com>||Thu Mar 12 18:20:35 2015 +0000|
flag: nicer usage messages Make PrintDefaults print an easier-to-read format, and allow the user to control it a bit by putting a hint into the usage string. Here is the new doc comment for PrintDefaults, which does the work: PrintDefaults prints, to standard error unless configured otherwise, a usage message showing the default settings of all defined command-line flags. For an integer valued flag x, the default output has the form -x int usage-message-for-x (default 7) The usage message will appear on a separate line except for single- letter boolean flags. Boolean flags omit the type, since they can be used without an actual value, and the parenthetical default is omitted if the default is the zero value for the type. The type, here int, can be replaced by a string of the user's choosing by placing in the usage string for the flag a back-quoted name; the first such item in the message is taken to be a parameter name to show in the message and the back quotes are stripped from the message when displayed. For instance, given flag.String("I", "", "search `directory` for include files") the output will be -I directory search directory for include files. Given A = flag.Bool("A", false, "for bootstrapping, allow 'any' type") B = flag.Bool("Alongflagname", false, "disable bounds checking") C = flag.Bool("C", true, "a boolean defaulting to true") D = flag.String("D", "", "set relative `path` for local imports") F = flag.Float64("F", 2.7, "a non-zero float") G = flag.Float64("G", 0, "a float that defaults to zero") N = flag.Int("N", 27, "a non-zero int") Z = flag.Int("Z", 0, "an int that defaults to zero") T = flag.Duration("deltaT", 0, "a duration") the old output was -A=false: for bootstrapping, allow 'any' type -Alongflagname=false: disable bounds checking -C=true: a boolean defaulting to true -D="": set relative `path` for local imports -F=2.7: a non-zero float -G=0: a float that defaults to zero -N=27: a non-zero int -Z=0: an int that defaults to zero -deltaT=0: a duration and the new output is -A for bootstrapping, allow 'any' type -Alongflagname disable bounds checking -C a boolean defaulting to true (default true) -D path set relative path for local imports -F float a non-zero float (default 2.7) -G float a float that defaults to zero -N int a non-zero int (default 27) -Z int an int that defaults to zero -deltaT duration a duration Change-Id: I54ab3cd5610d551422b004d95ab78305e06a395d Reviewed-on: https://go-review.googlesource.com/7330 Reviewed-by: Andrew Gerrand <firstname.lastname@example.org> Reviewed-by: Russ Cox <email@example.com>
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