1GETSUBOPT(3P)              POSIX Programmer's Manual             GETSUBOPT(3P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
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11

NAME

13       getsubopt — parse suboption arguments from a string
14

SYNOPSIS

16       #include <stdlib.h>
17
18       int getsubopt(char **optionp, char * const *keylistp, char **valuep);
19

DESCRIPTION

21       The getsubopt() function shall parse  suboption  arguments  in  a  flag
22       argument. Such options often result from the use of getopt().
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24       The  getsubopt()  argument  optionp  is  a  pointer to a pointer to the
25       option argument string. The suboption arguments shall be  separated  by
26       <comma>  characters and each may consist of either a single token, or a
27       token-value pair separated by an <equals-sign>.
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29       The keylistp argument shall be a pointer to a vector  of  strings.  The
30       end  of  the  vector is identified by a null pointer. Each entry in the
31       vector is one of the possible tokens that might be found  in  *optionp.
32       Since  <comma>  characters delimit suboption arguments in optionp, they
33       should not appear in any of the strings pointed to by keylistp.   Simi‐
34       larly,  because  an <equals-sign> separates a token from its value, the
35       application should not include an <equals-sign> in any of  the  strings
36       pointed  to by keylistp.  The getsubopt() function shall not modify the
37       keylistp vector.
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39       The valuep argument is the address of a value string pointer.
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41       If a <comma> appears in optionp, it shall be interpreted as a suboption
42       separator.  After  <comma> characters have been processed, if there are
43       one or more <equals-sign> characters in a suboption string,  the  first
44       <equals-sign> in any suboption string shall be interpreted as a separa‐
45       tor between a token and a value. Subsequent <equals-sign> characters in
46       a suboption string shall be interpreted as part of the value.
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48       If the string at *optionp contains only one suboption argument (equiva‐
49       lently, no <comma> characters), getsubopt() shall  update  *optionp  to
50       point  to  the  null  character at the end of the string. Otherwise, it
51       shall isolate the suboption argument by replacing the <comma> separator
52       with  a null character, and shall update *optionp to point to the start
53       of the next suboption argument. If the suboption argument has an  asso‐
54       ciated  value  (equivalently,  contains  an <equals-sign>), getsubopt()
55       shall update *valuep to point to the value's first  character.   Other‐
56       wise,  it  shall set *valuep to a null pointer. The calling application
57       may use this information to determine whether the presence  or  absence
58       of a value for the suboption is an error.
59
60       Additionally,  when  getsubopt()  fails to match the suboption argument
61       with a token in the keylistp  array,  the  calling  application  should
62       decide  if  this  is  an error, or if the unrecognized option should be
63       processed in another way.
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RETURN VALUE

66       The getsubopt() function shall return the index of  the  matched  token
67       string, or −1 if no token strings were matched.
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ERRORS

70       No errors are defined.
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72       The following sections are informative.
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EXAMPLES

75   Parsing Suboptions
76       The  following  example  uses the getsubopt() function to parse a value
77       argument in  the  optarg  external  variable  returned  by  a  call  to
78       getopt().
79
80           #include <stdio.h>
81           #include <stdlib.h>
82           #include <unistd.h>
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84           int do_all;
85           const char *type;
86           int read_size;
87           int write_size;
88           int read_only;
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90           enum
91           {
92               RO_OPTION = 0,
93               RW_OPTION,
94               READ_SIZE_OPTION,
95               WRITE_SIZE_OPTION
96           };
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98           const char *mount_opts[] =
99           {
100               [RO_OPTION] = "ro",
101               [RW_OPTION] = "rw",
102               [READ_SIZE_OPTION] = "rsize",
103               [WRITE_SIZE_OPTION] = "wsize",
104               NULL
105           };
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107           int
108           main(int argc, char *argv[])
109           {
110               char *subopts, *value;
111               int opt;
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113               while ((opt = getopt(argc, argv, "at:o:")) != -1)
114                   switch(opt)
115                       {
116                       case 'a':
117                           do_all = 1;
118                           break;
119                       case 't':
120                           type = optarg;
121                           break;
122                       case 'o':
123                           subopts = optarg;
124                           while (*subopts != ' ')
125                           {
126                               char *saved = subopts;
127                               switch(getsubopt(&subopts, (char **)mount_opts,
128                                   &value))
129                               {
130                               case RO_OPTION:
131                                   read_only = 1;
132                                   break;
133                               case RW_OPTION:
134                                   read_only = 0;
135                                   break;
136                               case READ_SIZE_OPTION:
137                                   if (value == NULL)
138                                       abort();
139                                   read_size = atoi(value);
140                                   break;
141                               case WRITE_SIZE_OPTION:
142                                   if (value == NULL)
143                                       abort();
144                                   write_size = atoi(value);
145                                   break;
146                               default:
147                                   /* Unknown suboption. */
148                                   printf("Unknown suboption `%s'\n", saved);
149                                   abort();
150                               }
151                           }
152                           break;
153                       default:
154                           abort();
155                       }
156
157               /* Do the real work. */
158
159               return 0;
160           }
161
162       If the above example is invoked with:
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164           program -o ro,rsize=512
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166       then  after option parsing, the variable do_all will be 0, type will be
167       a null pointer, read_size will  be  512,  write_size  will  be  0,  and
168       read_only will be 1. If it is invoked with:
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170           program -o oops
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172       it will print:
173
174           "Unknown suboption `oops'"
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176       before aborting.
177

APPLICATION USAGE

179       The  value  of *valuep when getsubopt() returns −1 is unspecified. His‐
180       torical implementations  provide  various  incompatible  extensions  to
181       allow an application to access the suboption text that was not found in
182       the keylistp array.
183

RATIONALE

185       The keylistp argument of getsubopt() is typed as  char  *  const  *  to
186       match  historical  practice. However, the standard is clear that imple‐
187       mentations will not modify either the array or the strings contained in
188       the array, as if the argument had been typed const char * const *.
189

FUTURE DIRECTIONS

191       None.
192

SEE ALSO

194       getopt()
195
196       The Base Definitions volume of POSIX.1‐2008, <stdlib.h>
197
199       Portions  of  this text are reprinted and reproduced in electronic form
200       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
201       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
202       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
203       cal  and  Electronics  Engineers,  Inc  and  The  Open Group.  (This is
204       POSIX.1-2008 with the 2013 Technical Corrigendum  1  applied.)  In  the
205       event of any discrepancy between this version and the original IEEE and
206       The Open Group Standard, the original IEEE and The Open Group  Standard
207       is  the  referee document. The original Standard can be obtained online
208       at http://www.unix.org/online.html .
209
210       Any typographical or formatting errors that appear  in  this  page  are
211       most likely to have been introduced during the conversion of the source
212       files to man page format. To report such errors,  see  https://www.ker
213       nel.org/doc/man-pages/reporting_bugs.html .
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217IEEE/The Open Group                  2013                        GETSUBOPT(3P)
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