regular test.

#include <iostream>

#include <stdio.h>

#include <stdlib.h>

#include <string>

#include <regex.h>

#include <assert.h>

#include <string.h>

using namespace std;

int find_first(string input, string pattern, string &out){

    regex_t reg;

    regmatch_t pm[1];

    int  iret = 0;

    out = "";

    /*编译正则表达式*/

    iret = regcomp(&reg, pattern.c_str(), REG_EXTENDED|REG_NEWLINE);

    if (iret != 0){

        return -1;

    }

    iret = regexec(&reg, input.c_str(), 1, pm, 0);

    if (iret == REG_NOMATCH){

        out = "";

        iret = input.length();

    }else if (iret != 0) {

        return -2;

    }else{

        out = input.substr(pm[0].rm_so,pm[0].rm_eo-pm[0].rm_so);

        iret = pm[0].rm_eo;

    }

    regfree(&reg);

    return iret;

}

int find_first(char *buff, char *pattern, char *outdata){

    regex_t reg;

    regmatch_t pm[1];

    int  status = 0;

    /*编译正则表达式*/

    status = regcomp(&reg, pattern, REG_EXTENDED|REG_NEWLINE);  //扩展正则表达式和识别换行符

    if (status != 0){    //成功返回0

        return -1;

    }

    status = regexec(&reg, buff, 1, pm, 0);

    if (status == REG_NOMATCH){

        printf("no match!\n");

        status = -1;

    }

    else if (status != 0) {

        return -2;

    }

    else if (status == 0) {

        int i, j;

        for (i = pm[0].rm_so, j = 0; i < pm[0].rm_eo; i++, j++) {

            outdata[j] = buff[i];

        }

        outdata[i] = '\0';

    }

    regfree(&reg);

    return status;

}

int find_all(char *buff, char *pattern, char result[][20]){   //返回匹配个数

    regex_t reg;

    regmatch_t pm[1];

    int  status = 0;

    char * p = buff;

    int count = 0;

    /*编译正则表达式*/

    status = regcomp(&reg, pattern, REG_EXTENDED|REG_NEWLINE);  //扩展正则表达式和识别换行符

    if (status != 0){    //成功返回0

        return -1;

    }

    int i = 0, j, k;

    while((status = regexec(&reg, p, 1, pm, 0)) == 0) {

        for(j = pm[0].rm_so, k = 0; j < pm[0].rm_eo; j++) {

            result[i][k++] = p[j];

        }

        result[i][k] = '\0';

        i++;

        p += pm[0].rm_eo;

        count++;

        if (*p == '\0')  break;

    }

    regfree(&reg);

    return count;

}

int print_file(const char *file_name, const char *pattern)

{

    regex_t reg;

    regmatch_t pm[1];

    int  status = 0;

    int count = 0;

    FILE *fp = fopen(file_name, "r+");

    assert(fp);

    char buff[1024] = {0};

    char output[1024] = {0};

    /*编译正则表达式*/

    status = regcomp(&reg, pattern, REG_EXTENDED|REG_NEWLINE);  //扩展正则表达式和识别换行符

    assert(status == 0);

    while(fgets(buff, sizeof(buff), fp)) {     //循环读取文件

        char * p = buff;

        while(1) {

            status = regexec(&reg, p, 1, pm, 0);

            if (status == 0) {  //匹配成功

                count++;

                strncpy(output, p + pm[0].rm_so, pm[0].rm_eo - pm[0].rm_so);

                cout<<"匹配:"<<output<<endl;

                p += pm[0].rm_eo;

            }

            else {

                break;

            }

        }

    }

    regfree(&reg);

    return count;

}

int main(int args, char *argv[])

{

    char result[20][20] = {0};

    char buf[] = "1231a4568b789c234";

    char pattern[] = "23";

    char resultfirst[20] = {0};

    if(args != 3)exit(-1);

    find_first(argv[1], argv[2], resultfirst);

    cout<<strlen(resultfirst) << ":" << resultfirst<<endl;

    cout << "***************************" <<endl;

    int count = find_all(argv[1], argv[2], result);

    for (int i = 0; i < count; i++) {

        cout<<"result:"<<"i="<<i+1<<"----"<<result[i]<<endl;

    }

    cout << "***************************" <<endl;

    count = print_file("test.txt", "[0-9]{5}");

    cout<<"匹配的个数:"<<count<<endl;

    return 0;

}