10564b1175
groff 1.23.0 added .MR to its -man macro package. The NEWS file states
that the inclusion of the macro "was prompted by its introduction to
Plan 9 from User Space's troff in August 2020." From d32deab it seems
that the name for Plan 9 from User Space's implementation was suggested
by groff maintainer G. Brandon Robinson.
Not sure if the intention was to make these definitions compatible, but
it would be nice if they were.
Currently, Plan 9 from User Space's .MR expects its second argument to
be parenthesized. groff's .MR does not. This results in extra
parentheses appearing in manual references when viewing Plan 9 from User
Space's manual pages on a system using groff.
120 lines
2.0 KiB
Groff
120 lines
2.0 KiB
Groff
.TH 9P-CMDBUF 3
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.SH NAME
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Cmdbuf, parsecmd, respondcmderror, lookupcmd \- control message parsing
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.SH SYNOPSIS
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.ft L
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.nf
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#include <u.h>
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#include <libc.h>
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#include <fcall.h>
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#include <thread.h>
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#include <9p.h>
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.fi
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.PP
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.ft L
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.nf
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.ta \w'\fL1234'u +\w'\fL12345678'u
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typedef struct Cmdbuf
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{
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char *buf;
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char **f;
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int nf;
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} Cmdbuf;
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typedef struct Cmdtab
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{
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int index;
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char *cmd;
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int narg;
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};
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Cmdbuf *parsecmd(char *p, int n)
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Cmdtab *lookupcmd(Cmdbuf *cb, Cmdtab *tab, int ntab)
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void respondcmderror(Req *r, Cmdbuf *cb, char *fmt, ...)
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.fi
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.SH DESCRIPTION
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These data structures and functions provide parsing of textual control messages.
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.PP
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.I Parsecmd
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treats the
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.I n
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bytes at
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.I p
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(which need not be NUL-terminated) as a UTF string and splits it
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using
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.I tokenize
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(see
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.MR getfields 3 ).
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It returns a
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.B Cmdbuf
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structure holding pointers to each field in the message.
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.PP
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.I Lookupcmd
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walks through the array
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.IR ctab ,
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which has
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.I ntab
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entries,
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looking for the first
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.B Cmdtab
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that matches the parsed command.
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(If the parsed command is empty,
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.I lookupcmd
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returns nil immediately.)
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A
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.B Cmdtab
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matches the command if
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.I cmd
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is equal to
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.IB cb -> f [0]
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or if
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.I cmd
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is
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.LR * .
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Once a matching
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.B Cmdtab
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has been found, if
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.I narg
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is not zero, then the parsed command
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must have exactly
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.I narg
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fields (including the command string itself).
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If the command has the wrong number of arguments,
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.I lookupcmd
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returns nil.
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Otherwise, it returns a pointer to the
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.B Cmdtab
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entry.
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If
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.I lookupcmd
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does not find a matching command at all,
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it returns nil.
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Whenever
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.I lookupcmd
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returns nil, it sets the system error string.
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.PP
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.I Respondcmderror
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resoponds to request
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.I r
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with an error of the form
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`\fIfmt\fB:\fI cmd\fR,'
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where
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.I fmt
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is the formatted string and
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.I cmd
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is a reconstruction of the parsed command.
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Fmt
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is often simply
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.B "%r" .
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.SH EXAMPLES
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This interface is not used in any distributed 9P servers.
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It was lifted from the Plan 9 kernel.
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Almost any Plan 9 kernel driver
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.RB ( /sys/src/9/*/dev*.c
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on Plan 9)
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is a good example.
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.SH SOURCE
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.B \*9/src/lib9p/parse.c
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.SH SEE ALSO
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.MR 9p 3
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