C语言 逆序显示文本内容并保存

【说明】

    对指定文件中的内容或传入的字符串参数逆序打印并保存到文件中。

【命令行示例】

    [root@localhost]$ ./reverseStr test.txt

    这条命令的含义是读取 ./test.txt 文件中的内容，将文件内容顺序反向存储到 outPut.txt 文件中。

    [root@localhost]$ ./reverseStr "Hello world"

    这条命令的含义是将 "Hello world" 逆序打印到控制台，并存储到文件 outPut.txt 文件中。

【源码】

#include <stdio.h>#include <string.h>#include <stdlib.h>int main(char argc, char **argv){    FILE *pFileRead = NULL;    char *pstrTarget = NULL;    char cRead;    unsigned long ulCountWord = 0;    char *pstrContent = NULL;    char *pstrReverse = NULL;    FILE *pFileOutput = NULL;        if(argc == 2){        pstrTarget = argv[1];        if(strstr(pstrTarget, ".txt")){     // 传入参数是文件名            if(NULL == (pFileRead = fopen(pstrTarget, "r"))){                printf("open file %s error!\n", pstrTarget);            }else{                while(EOF != fscanf(pFileRead, "%c", &cRead)){                    ++ulCountWord;                }                printf("%ld bytes been read.\n", ulCountWord);                pstrContent = (char *)malloc((size_t)ulCountWord);                fseek(pFileRead, 0, SEEK_SET);                printf("%d items been read.\n", fread(pstrContent, sizeof(char), (size_t)ulCountWord, pFileRead));                pstrReverse = pstrContent;                printf("content: %s\n", pstrReverse);                pstrReverse += ulCountWord - 1;                if(NULL == (pFileOutput = fopen("outPut.txt", "w"))){                    printf("open file reverseOut.txt error!\n");                }else{                    for( ;ulCountWord > 0; ulCountWord--){                        fprintf(pFileOutput, "%c", *pstrReverse);                        --pstrReverse;                    }                    fprintf(pFileOutput, "%c", *pstrReverse);                    fclose(pFileOutput);                }                free(pstrContent);                fclose(pFileRead);            }        }else{      // 传入参数是字符串内容            ulCountWord = (unsigned long)strlen(pstrTarget);            pstrReverse = pstrTarget;            printf("content: %s\n", pstrReverse);            pstrReverse += ulCountWord;            for( ; ulCountWord > 0; ulCountWord--){                printf("%c", *pstrReverse);                --pstrReverse;            }            printf("%c\n", *pstrReverse);        }    }else{        printf("invalid argument, which should be a filename or a string.\n");    }    return 0;}