sysctl.c

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#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <syscall.h>
 
#include <sys/sysctl.h>
 
typedef struct SysCtlEntry {
    char        path[64];
    int         type;
    int         flags;
    char        description[128];
} SysCtlEntry;
 
#define SYSCTL_STR(_PATH, _FLAGS, _DESCRIPTION, _DEFAULT) \
    { #_PATH, SYSCTL_TYPE_STR, _FLAGS, _DESCRIPTION },
#define SYSCTL_INT(_PATH, _FLAGS, _DESCRIPTION, _DEFAULT) \
    { #_PATH, SYSCTL_TYPE_INT, _FLAGS, _DESCRIPTION },
#define SYSCTL_BOOL(_PATH, _FLAGS, _DESCRIPTION, _DEFAULT) \
    { #_PATH, SYSCTL_TYPE_BOOL, _FLAGS, _DESCRIPTION },
SysCtlEntry SYSCTLTable[] = {
    SYSCTL_LIST
    { "", 0, 0, "" },
};
#undef SYSCTL_STR
#undef SYSCTL_INT
#undef SYSCTL_BOOL
 
void
PrintVal(int idx)
{
    switch (SYSCTLTable[idx].type) {
        case SYSCTL_TYPE_STR: {
            SysCtlString scStr;
 
            OSSysCtl(SYSCTLTable[idx].path, &scStr, NULL);
            printf("%s: %s\n", SYSCTLTable[idx].path, scStr.value);
            break;
        }
        case SYSCTL_TYPE_INT: {
            SysCtlInt scInt;
 
            OSSysCtl(SYSCTLTable[idx].path, &scInt, NULL);
            printf("%s: %ld\n", SYSCTLTable[idx].path, scInt.value);
            break;
        }
        case SYSCTL_TYPE_BOOL: {
            SysCtlBool scBool;
 
            OSSysCtl(SYSCTLTable[idx].path, &scBool, NULL);
            printf("%s: %s\n", SYSCTLTable[idx].path,
                    scBool.value ? "true" : "false");
            break;
        }
        default:
            printf("%s: Unsupported type\n", SYSCTLTable[idx].path);
            break;
    }
}
 
void
UpdateVal(int idx, const char *val)
{
    switch (SYSCTLTable[idx].type) {
        case SYSCTL_TYPE_STR: {
            SysCtlString scStr;
 
            strncpy(scStr.value, val, sizeof(scStr.value) - 1);
            OSSysCtl(SYSCTLTable[idx].path, NULL, &scStr);
            break;
        }
        case SYSCTL_TYPE_INT: {
            SysCtlInt scInt;
 
            scInt.value = atoi(val);
            printf("%ld\n", scInt.value);
            OSSysCtl(SYSCTLTable[idx].path, NULL, &scInt);
            break;
        }
        case SYSCTL_TYPE_BOOL: {
            SysCtlBool scBool;
 
            if (strcmp(val,"true") == 0)
                scBool.value = true;
            else if (strcmp(val,"false") == 0)
                scBool.value = false;
            else {
                printf("Value must be true or false\n");
                exit(1);
            }
            OSSysCtl(SYSCTLTable[idx].path, NULL, &scBool);
            break;
        }
        default:
            printf("%s: Unsupported type\n", SYSCTLTable[idx].path);
            break;
    }
}
 
int
main(int argc, const char *argv[])
{
    if (argc == 2 && strcmp(argv[1],"-h") == 0) {
        printf("Usage: sysctl [NODE] [VALUE]\n");
        return 1;
    }
 
    if (argc == 2 && strcmp(argv[1],"-d") == 0) {
        printf("%-20s %s\n", "Name", "Description");
        for (int i = 0; SYSCTLTable[i].type != 0; i++) {
            printf("%-20s %s\n",
                    SYSCTLTable[i].path,
                    SYSCTLTable[i].description);
        }
        return 0;
    }
 
    if (argc == 2 || argc == 3) {
        for (int i = 0; SYSCTLTable[i].type != 0; i++) {
            if (strcmp(SYSCTLTable[i].path, argv[1]) == 0) {
                if (argc == 2)
                    PrintVal(i);
                else
                    UpdateVal(i, argv[2]);
            }
        }
 
        return 0;
    }
 
    for (int i = 0; SYSCTLTable[i].type != 0; i++) {
        PrintVal(i);
    }
 
    return 0;
}