getopt_long_only()我正在尝试与自定义错误消息一起使用。代码如下所示。我尝试设置 opterr=0 并在 optstring 开头使用冒号来禁用内置错误消息。我添加了一段用布尔值控制的代码块optoptWorks = true来尝试自定义错误消息，例如在-z使用错误选项时打印消息。但是optopt始终设置为 0 并且?我使用的错误消息没有意义。':'（冒号大小写）错误（缺少参数，例如-d）对于自定义消息确实可以正常工作。关闭内置错误消息并进行处理?似乎会导致optopt始终设置为 0，因此我无法打印有问题的选项 ( -z is not recognized)。我在 Debian Linux gcc 4.9.4 和 Cygwin gcc 7.3.0 上编译，两者都给出相同的结果。看起来getopt_long_only()可能设置不optopt正确或者我错过了什么？网络上的许多示例通过使用内置错误消息或仅打印用法而不告诉用户哪个选项无法识别来解决此问题。
这是输出optoptWorks=false：
$ ./testoptget -z
testoptget: unknown option -- z
-d # Set the debug level.
-h, --help Print program usage.
-q Run in quiet mode (log messages to syslog but not console).
-v, --version Print program version.
$ ./testoptget -d
testoptget: option requires an argument -- d
-d # Set the debug level.
-h, --help Print program usage.
-q Run in quiet mode (log messages to syslog but not console).
-v, --version Print program version.
这是输出optoptWorks=true：
$ ./testoptget -z
[ERROR] Unknown option character '\x0'.
-d # Set the debug level.
-h, --help Print program usage.
-q Run in quiet mode (log messages to syslog but not console).
-v, --version Print program version.
$ ./testoptget -d
[ERROR] Option '-d' is missing argument.
-d # Set the debug level.
-h, --help Print program usage.
-q Run in quiet mode (log messages to syslog but not console).
-v, --version Print program version.
代码如下：
/*
Test program for getopt_long_only
*/
#include <ctype.h>
#include <getopt.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
int debug = 0; /* Default to not debugging */
/**
Print the program usage.
*/
void usage(void)
{
/* Print the program name and version */
printf("\n");
printf("-d # Set the debug level.\n");
printf("-h, --help Print program usage.\n");
printf("-q Run in quiet mode (log messages to syslog but not console).\n");
printf("-v, --version Print program version.\n\n");
exit(0);
}
/**
Parse command line parameters and set data for program.
@param argc number of command line parameters
@param argv list of command line parameters
*/
void parseargs(int argc,char **argv)
{ /*
See: https://www.gnu.org/software/libc/manual/html_node/Getopt.html#Getopt
See: http://man7.org/linux/man-pages/man3/getopt.3.html
Because legacy -version and --version need to be supported, use getopts_long_only.
*/
/*
The meaning of the following is:
name - the name of the long option
has_arg - whether the option has an argument like --arg param or --arg=param
flag - the numeric value to return (set to "opt" below), if NULL or zero, return "val"
val - the value to return (set to "opt" below) if "flag" not set, use the one-character equivalent
*/
static struct option long_options[] = {
{ "help", no_argument, 0, 'h' }, /* returns as if -v, index not needed */
{ "version", no_argument, 0, 'v' }, /* returns as if -h, index not needed */
{ 0, 0, 0, 0 } /* last element of array must be zeros */
};
int long_index = 0;
int opt;
int errorCount = 0;
/* In <unistd.h>: external int optind, opterr, optopt */
bool optoptWorks = false; /* Apparently optopt gets set to 0 for unknown argument so let the getopt_long_only print the error */
char optstring[32] = "d:hqv";
if ( optoptWorks ) {
/*
If getopt_long_only works as it is supposed to...
Set opterr to zero so getopt calls won't print an error - check for errors in '?' return value
Also use : as first character of optstring to cause : to be used for error handling
*/
opterr = 0;
/* Do the following because strcat is not safe on overlapping strings */
char optstring2[32];
strcpy(optstring2,optstring);
strcpy(optstring,":");
strcat(optstring,optstring2);
}
while((opt = getopt_long_only(argc, argv, optstring, long_options, &long_index)) != -1) {
switch (opt) { /* Will match single character option or long_options val or flag */
case 'd':
/* -d #, Set the debug level to the argument value */
debug = atoi(optarg);
break;
case 'h':
/*
-h, print the usage and exit
-help
--help
*/
usage();
exit(0);
break;
case 'q':
/* -q, indicate that messages should not be printed to stdout */
break;
case 'v':
/*
-v, print the version via standard function,
-version
--version
*/
break;
case ':':
/*
This is an error indicator indicated by : at the start of get_opt_long 3rd argument.
Handle missing argument, such as -d but no argument.
*/
fprintf(stderr, "[ERROR] Option '-%c' is missing argument.\n", optopt);
++errorCount;
break;
case '?':
/*
Handle unknown parameters as per getopt man page example.
"optopt" should contain the offending argument, but perhaps matches last long argument (zero record).
Note that legacy ? command line parameter is no longer supported.
*/
if (isprint(optopt)) {
/* Printable character so print it in the warning. */
if ( optoptWorks ) {
fprintf(stderr, "[ERROR] Unknown option '-%c'.\n", optopt);
}
++errorCount;
}
else {
/* Nonprintable character so show escape sequence. */
if ( optoptWorks ) {
fprintf(stderr, "[ERROR] Unknown option character '\\x%x'.\n", optopt);
}
++errorCount;
}
break;
} /* end switch */
} /* end while */
if ( errorCount > 0 ) {
usage();
exit(1);
}
}
/**
Main program.
@param argc number of command line parameters
@param argv list of command line parameters
@param arge list of environment variables
*/
int main(int argc,char **argv,char **arge)
{
/* Parse command arguments */
parseargs(argc,argv);
/* Normal program termination */
return(0);
}
optopt当发现未知的长选项时，确实设置为零，请参见此处。然而在我看来，您可以使用optind - 1作为索引来argv打印有问题的选项，因为在returns之前在这里optind递增。getopt'?'
据我了解，您的目标只是指定自定义错误消息。
同样来自 man getopt_long：
如果 optstring 的第一个字符（跟在上述任何可选的“+”或“-”之后）是冒号（“:”），则 getopt() 同样不会打印错误消息。此外，它返回“:”而不是“?” 指示缺少的选项参数。这允许调用者区分两种不同类型的错误。
您引用的文档不是getopt关于getopt_long_only. man getopt_long_only确实这么说，getopt_long() function works like getopt()但optopt被设置为“选项字符”。如果选项很长，则没有“选项字符”，而是一个“选项字符串”（我会这样称呼它）-在我看来，设置optopt为零是合乎逻辑的。
因此，根据 optstring 中的初始字符，返回:or ，如此处和此处和此处实现的那样。?
以下程序是您的程序，删除了注释，缩短了使用功能，仅用以下内容替换exit并return添加了打印违规选项printf("%s", argv[opting - 1]);：
#include <ctype.h>
#include <getopt.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
int debug = 0;
void usage(void) { printf("-- insert usage here --\n"); }
void parseargs(int argc,char **argv)
{
static struct option long_options[] = {
{ "help", no_argument, 0, 'h' },
{ "version", no_argument, 0, 'v' },
{ 0, 0, 0, 0 }
};
int long_index = 0;
int opt;
int errorCount = 0;
optind = 1;
while((opt = getopt_long_only(argc, argv, ":d:hqv", long_options, &long_index)) != -1) {
switch (opt) {
case 'd':
debug = atoi(optarg);
break;
case 'h':
usage();
return;
break;
case 'q':
break;
case 'v':
break;
case ':':
fprintf(stderr, "[ERROR] Option '-%c' is missing argument.\n", optopt);
++errorCount;
break;
case '?':
if (optopt == 0) {
fprintf(stderr, "[ERROR] Unknown option '%s'.\n", argv[optind - 1]);
} else {
fprintf(stderr, "[ERROR] Error parsing option '-%c'\n", optopt);
}
++errorCount;
break;
}
}
if ( errorCount > 0 ) {
usage();
return;
}
}
int main(int argc, char **argv)
{
#define SIZE(x) (sizeof(x)/sizeof(*x))
struct {
int argc;
char **argv;
} tests[] = {
{ 2, (char*[]){ argv[0], (char[]){"-z"}, NULL, } },
{ 2, (char*[]){ argv[0], (char[]){"-d"}, NULL, } },
};
for (int i = 0; i < SIZE(tests); ++i) {
printf("\n## test tests[i].argv[1] = %s\n", tests[i].argv[1]);
parseargs(tests[i].argc, tests[i].argv);
}
return 0;
}
输出：
## test tests[i].argv[1] = -z
[ERROR] Unknown option '-z'.
-- insert usage here --
## test tests[i].argv[1] = -d
[ERROR] Option '-d' is missing argument.
-- insert usage here --
如果 optstring 设置为"d:hqv"没有前导:，那么它就属于这种?情况，即。然后程序返回：
## test tests[i].argv[1] = -z
./a.out: unrecognized option '-z'
[ERROR] Unknown option '-z'.
-- insert usage here --
## test tests[i].argv[1] = -d
./a.out: option requires an argument -- 'd'
[ERROR] Error parsing option '-d'
-- insert usage here --