1IPSEC_OPTIONSFROM(3) Library Functions Manual IPSEC_OPTIONSFROM(3)
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6 ipsec optionsfrom - read additional ``command-line'' options from file
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9 #include <freeswan.h>
10 const char *optionsfrom(char *filename, int *argcp,
12 char ***argvp, int optind, FILE *errsto);
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15 Optionsfrom is called from within a getopt_long(3) scan, as the result
16 of the appearance of an option (preferably --optionsfrom) to insert
17 additional ``command-line'' arguments into the scan immediately after
18 the option. Typically this would be done to pick up options which are
19 security-sensitive and should not be visible to ps(1) and similar com‐
20 mands, and hence cannot be supplied as part of the actual command line
21 or the environment.
22 Optionsfrom reads the additional arguments from the specified filename,
24 allocates a new argument vector to hold pointers to the existing argu‐
25 ments plus the new ones, and amends argc and argv (via the pointers
26 argcp and argvp, which must point to the argc and argv being supplied
27 to getopt_long(3)) accordingly. Optind must be the index, in the orig‐
28 inal argument vector, of the next argument.
29 If errsto is NULL, optionsfrom returns NULL for success and a pointer
31 to a string-literal error message for failure; see DIAGNOSTICS. If
32 errsto is non-NULL and an error occurs, optionsfrom prints a suitable
33 complaint onto the errsto descriptor and invokes exit with an exit sta‐
34 tus of 2; this is a convenience for cases where more sophisticated
35 responses are not required.
36 The text of existing arguments is not disturbed by optionsfrom, so
38 pointers to them and into them remain valid.
39 The file of additional arguments is an ASCII text file. Lines consist‐
41 ing solely of white space, and lines beginning with #, are comments and
42 are ignored. Otherwise, a line which does not begin with - is taken to
43 be a single argument; if it both begins and ends with double-quote ("),
44 those quotes are stripped off (note, no other processing is done within
45 the line!). A line beginning with - is considered to contain multiple
46 arguments separated by white space.
47 Because optionsfrom reads its entire file before the getopt_long(3)
49 scan is resumed, an optionsfrom file can contain another --optionsfrom
50 option. Obviously, infinite loops are possible here. If errsto is
51 non-NULL, optionsfrom considers it an error to be called more than 100
52 times. If errsto is NULL, loop detection is up to the caller (and the
53 internal loop counter is zeroed out).
54
56 A reasonable way to invoke optionsfrom would be like so:
57 #include <getopt.h>
59 struct option opts[] = {
61 /* ... */
62 "optionsfrom", 1, NULL, '+',
63 /* ... */
64 };
65 int
67 main(argc, argv)
68 int argc;
69 char *argv[];
70 {
71 int opt;
72 extern char *optarg;
73 extern int optind;
74 while ((opt = getopt_long(argc, argv, "", opts, NULL)) != EOF)
76 switch (opt) {
77 /* ... */
78 case '+': /* optionsfrom */
79 optionsfrom(optarg, &argc, &argv, optind, stderr);
80 /* does not return on error */
81 break;
82 /* ... */
83 }
84 /* ... */
85
87 getopt_long(3)
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90 Errors in optionsfrom are: unable to open file; attempt to allocate
91 temporary storage for argument or argument vector failed; read error in
92 file; line too long.
93
95 Written for the FreeS/WAN project by Henry Spencer.
96
98 The double-quote convention is rather simplistic.
99 Line length is currently limited to 1023 bytes, and there is no contin‐
101 uation convention.
102 The restriction of error reports to literal strings (so that callers
104 don't need to worry about freeing them or copying them) does limit the
105 precision of error reporting.
106 The error-reporting convention lends itself to slightly obscure code,
108 because many readers will not think of NULL as signifying success.
109 There is a certain element of unwarranted chumminess with the insides
111 of getopt_long(3) here. No non-public interfaces are actually used,
112 but optionsfrom does rely on getopt_long(3) being well-behaved in cer‐
113 tain ways that are not actually promised by the specs.
114 16 Oct 1998 IPSEC_OPTIONSFROM(3)