Using the flag package to parse custom strings
Alexander Orlov
the parsing schema of the flag package. But the string isn't provided
to the Go binary from the initialization on. I want to parse arbitrary
strings during runtime. However AFAIK the flag package has no function
to set a base string during runtime that can be parsed later?
Doing
var flagvar int
flag.IntVar(&flagvar, "flagname", 1234, "help message for flagname")
in my function I get a runtime error. Also it's not really what I
want. I want to
1. provide a base string (containing parameters with values and value-
less params/"switches")
2. get all parameters of this base string
3. get all values for each parameter
4. get the count of all params
5. get the count of all values of a single parameter
Can I do it using the flag package or is there another package you'd
recommend?
Kyle Lemons
I want to extract commands and parameters from a string according to
the parsing schema of the flag package. But the string isn't provided
to the Go binary from the initialization on. I want to parse arbitrary
strings during runtime. However AFAIK the flag package has no function
to set a base string during runtime that can be parsed later?
Doing
var flagvar int
flag.IntVar(&flagvar, "flagname", 1234, "help message for flagname")
in my function I get a runtime error. Also it's not really what I
want. I want to
1. provide a base string (containing parameters with values and value-
less params/"switches")
2. get all parameters of this base string
3. get all values for each parameter
4. get the count of all params
5. get the count of all values of a single parameter
Can I do it using the flag package or is there another package you'd
recommend?
--
~Kyle
— Brian Kernighan
Alexander Orlov
> On Tue, May 17, 2011 at 12:50 PM, Alexander Orlov <alexander.or...@loxal.net
> > less params/"switches")
>
> This is the only thing that isn't done by the flag package. However, if you
> split your string yourself and assign it to os.Args, you can emulate this
> behavior. The real question is WHY you need this. Command-line flags are
> an efficient way of passing arguments to a program by hand, but not always
> the best way to get them from other places.
pass a r.URL.Raw that can look like "/command%20--param%20value%20--
param1%20value1%20--paramSwitch". I know that passing a JSON is a
better way to communicate with a RESTful API but for humans entering
JSON-wrapped commands isn't the best solution. So I want to parse this
r.URL.Raw or r.FormValue("commandWithParams") with the flag package
but modifying Appengine's os.Args isn't the best solution I guess. So
I can't use the flag package to parse this kind of commands?
Kyle Lemons
own? If it doesn't, then you can do what I described: Split the
string by space (after urldecoding) and give it to os.Args.
It would also be a trivial CL to add functionality to the flag package
to add a flag.ParseStrings(args[] string). Or even a
flag.ParseString(cli string), but with IFS issues I think the former
would be preferential. I don't know if it would be accepted or not,
though.
The better way might be to sit down with your "/command"s and figure
out some logical "path names" for your use cases. This is similar,
but not identical to, designing a RESTful API (which makes the URIs
into entity names and uses the HTTP methods GET, POST, etc to modify
or query them). For example,
/users - list by default
/users/list - list explicitly
/users/list?from=20100408 - list users who registered on or after a date
/users/add?name=foo&password=bar - add a user
These URLs make a lot of sense to someone who's reading them, don't
have URLencoded spaces to deal with, and are not difficult to type.
--
Alexander Orlov
> It would also be a trivial CL to add functionality to the flag package
> to add a flag.ParseStrings(args[] string). Or even a
> flag.ParseString(cli string), but with IFS issues I think the former
> would be preferential. I don't know if it would be accepted or not,
> though.
functionality isn't provided out-of-the-box. Or is the CLI not
considered as a good (web) UI replacement anymore...? I'm so fast
working with the CLI — why not bringing it to the web?
> /users - list by default
> /users/list - list explicitly
> /users/list?from=20100408 - list users who registered on or after a date
> /users/add?name=foo&password=bar - add a user
thing for machines and devs, not for non-devs. I take the command and
its params from http.Request.URL.Raw only in the first step. Later the
whole command string can come from anywhere. So I really need the flag
pkg and without the os.Args default.
André Moraes
valid argument array.
Note that it break in spaces while it shoud check for arguments on
quotes, and it can't handle unix-like arguments.
But is a start. :)
/**
Author: Andre Luiz Alves Moraes
Barbacena - MG - Brasil
*/
package main
import (
"bytes"
"fmt"
)
func main() {
argument := "-param1 value -param2 other rest of the string"
argv := make([]string, 1)
buff := bytes.NewBufferString(argument)
for {
rune, _, _ := buff.ReadRune()
if rune == '-' {
arg, _ := buff.ReadString(' ')
val, _ := buff.ReadString(' ')
argv = append(argv, arg, val)
} else {
rest := string(rune) + buff.String()
argv = append(argv, rest)
break
}
if buff.Len() == 0 {
break
}
}
fmt.Printf("argv: %v\n", argv)
}
--
André Moraes
http://andredevchannel.blogspot.com/
André Moraes
Alexander Orlov
I wrote a very simple test program, that breaks the string into a
valid argument array.
roger peppe
strings.Fields provides the above functionality.
you might be able to get the scanner package to help
you parse quoted strings.
André Moraes
>> Very nice, thx. However to have a correspoinding functionality within Go's
>> standard pkgs would be nice.
>
> strings.Fields provides the above functionality.
> you might be able to get the scanner package to help
> you parse quoted strings.
>
string.Fiels break only on the spaces.
My code break on spaces only for the arguments switches.
When the code don't find a "-" as the rune, it reads the rest of the
line as single string (maybe that isn't the best behavior) but is
different from string.Fields.
Also, scanner package definitely will be a best tool for this parsing job.