🦄 refactor(C14, C15):

C14-文件系统/fs/100days.c

@@ -0,0 +1,34 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+#define TIMESTRSIZE 128
+
+/**
+ * @brief    找出100天以后是哪一天
+ * @details
+ *
+ * @param    argc
+ * @param    argv
+ *
+ * @return  int
+ */
+int main(int argc, char **argv)
+{
+    time_t     stamp;
+    struct tm *tm;
+    char       timestr[TIMESTRSIZE];
+
+    time(&stamp);
+    tm = localtime(&stamp);
+    strftime(timestr, TIMESTRSIZE, "Now: %Y-%m-%d", tm);
+    puts(timestr);
+
+    tm->tm_mday += 100;
+    //  mktime 会先调整tm溢出的情况
+    mktime(tm);
+    strftime(timestr, TIMESTRSIZE, "100 days later: %Y-%m-%d", tm);
+    puts(timestr);
+
+    exit(0);
+}

C14-文件系统/fs/W_process_excel.c

@@ -0,0 +1,205 @@
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#if 1
+#    define debug(fmt, args...) printf(fmt, ##args)
+#else
+#    define debug(fmt, args...)
+#endif
+
+/**
+ * @brief    读取一行
+ * @details
+ *           循环读入一个字符
+ *           如何判断读完一行? 读到0x0d, 0x0a
+ *
+ * @param    fd
+ * @param    buf
+ *
+ * @return  int 读到的一行数据的数据个数( n>=0 )
+ *              -1: 读到文件尾部或者出错
+ */
+static int read_line(int fd, unsigned char *buf)
+{
+    unsigned char c;
+    int           len;
+    int           i   = 0;
+    int           err = 0;
+
+    while (1)
+    {
+        len = read(fd, &c, 1);
+        if (len <= 0)
+        {
+            err = -1;
+            break;
+        }
+        else
+        {
+            if (c != '\n' && c != '\r')
+            {
+                buf[i] = c;
+                i++;
+            }
+            else /* 碰到回车换行 */
+            {
+                err = 0;
+                break;
+            }
+        }
+    }
+
+    buf[i] = '\0';
+
+    if (err && (0 == i))
+        /* 读到文件尾部且无有效数据 */
+        return -1;
+    else
+        return i;
+}
+
+/**
+ * @brief    处理一行的数据, 计算出总分和评价
+ * @details
+ *
+ * @param    data_buf
+ * @param    result_buf
+ *
+ * @return  int
+ */
+static void process_data(unsigned char *data_buf, unsigned char *result_buf)
+{
+    /**
+     *   eg1: data_buf=",语文,数学,英语,总分,评价"
+     *      result_buf=",语文,数学,英语,总分,评价"
+     *
+     *   eg2: data_buf="张三,90,91,92,,"
+     *      result_buf="张三,90,91,92,273,A+"
+     *
+     */
+
+    char  name[100];
+    int   scores[3];
+    int   sum;
+    char *levels[] = {"A+", "A", "B"};
+    int   level;
+
+    // debug("data_buf[0]: %x\n", data_buf[0]);
+    if (0xef == data_buf[0]) /* 对于UTF-8, 前三个字符是0xef 0xbb 0xbf */
+    {
+        strcpy(result_buf, data_buf);
+    }
+    else
+    {
+        // debug("data_buf: %s\n", data_buf);
+        // debug("进入了\n");
+        /**
+         * @brief    从字符串得到数据
+         * @details
+         *           拆分信息: scanf分隔符
+         *           %[^,]: 读数据直到碰到逗号
+         *
+         */
+        sscanf(data_buf,
+               "%[^,],%d,%d,%d,,",
+               name,
+               &scores[0],
+               &scores[1],
+               &scores[2]);
+
+        debug("name: %s, scores: %d, %d, %d\n",
+              name,
+              scores[0],
+              scores[1],
+              scores[2]);
+
+        sum = scores[0] + scores[1] + scores[2];
+        if (sum >= 270)
+            level = 0;
+        else if (sum >= 240)
+            level = 1;
+        else
+            level = 2;
+
+        sprintf(result_buf,
+                "%s,%d,%d,%d,%d,%s",
+                name,
+                scores[0],
+                scores[1],
+                scores[2],
+                sum,
+                levels[level]);
+    }
+}
+
+
+/**
+ * @brief    处理csv表格
+ * @details
+ *           Usage: ./W_process_excel data.csv result.csv
+ *
+ * @param    argc
+ * @param    argv
+ *
+ * @return  int
+ */
+int main(int argc, char **argv)
+{
+    int           fd_data, fd_result;
+    int           len;
+    unsigned char data_buf[1000];
+    unsigned char result_buf[1000];
+
+    if (argc != 3)
+    {
+        printf("Usage: %s data.csv result.csv\n", argv[0]);
+        exit(1);
+    }
+
+    fd_data = open(argv[1], O_RDONLY);
+    if (fd_data < 0)
+    {
+        perror("open data.csv");
+        exit(1);
+    }
+    else
+        printf("data file fd: %d\n", fd_data);
+
+    fd_result = open(argv[2], O_WRONLY | O_CREAT | O_TRUNC, 0644);
+    if (fd_result < 0)
+    {
+        perror("open result.csv");
+        exit(1);
+    }
+    else
+        printf("result file fd: %d\n", fd_result);
+
+    while (1)
+    {
+        /* 读取1行 */
+        len = read_line(fd_data, data_buf);
+        if (-1 == len)
+            break;
+
+        // if (len != 0)
+        //     debug("%s\n\r", data_buf);
+
+        if (len != 0)
+        {
+            /* 处理1行 */
+            process_data(data_buf, result_buf);
+
+            /* 写入结果文件 */
+            write(fd_result, result_buf, strlen(result_buf));
+            write(fd_result, "\r\n", 2);
+        }
+    }
+
+    close(fd_data);
+    close(fd_result);
+
+    exit(0);
+}

C14-文件系统/fs/atexit.c

@@ -0,0 +1,37 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+static void f1(void)
+{
+    puts("f1() is working!");
+}
+
+static void f2(void)
+{
+    puts("f2() is working!");
+}
+
+static void f3(void)
+{
+    puts("f3() is working!");
+}
+
+int main(int argc, char **argv)
+{
+    puts("Begin!");
+
+    atexit(f1);
+    atexit(f2);
+    atexit(f3);
+
+    puts("End!");
+
+    exit(0);
+}
+// out:
+// *[main][~/Linux-C-Notes/C13-Linux系统编程/fs]$ ./atexit
+// Begin!
+// End!
+// f3() is working!
+// f2() is working!
+// f1() is working!

C14-文件系统/fs/big.c

@@ -0,0 +1,34 @@
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+int main(int argc, char **argv)
+{
+    if (argc < 2)
+    {
+        fprintf(stderr, "Usage:...\n");
+        exit(1);
+    }
+
+    int fd;
+
+    fd = open(argv[1], O_WRONLY | O_CREAT | O_TRUNC, 0600);
+    if (fd < 0)
+    {
+        perror("open()");
+        exit(1);
+    }
+
+    // 生成一个5G的文件
+    // !!! 整数溢出
+    lseek(fd, 5LL * 1024LL * 1024LL * 1024LL - 1LL, SEEK_SET);
+
+    // 写入尾0
+    write(fd, "", 1);
+
+    close(fd);
+    exit(0);
+}

C14-文件系统/fs/check.c

@@ -0,0 +1,46 @@
+#include <crypt.h>
+#include <shadow.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+/**
+ * @brief    加密输入的密码并与shadow文件中的密码进行比较
+ * @details
+ *        !!! compile: gcc check.c -o check -lcrypt
+ *        !!! 需要root权限运行
+ *
+ * @param    argc
+ * @param    argv   [in]  用户名
+ *
+ * @return  int
+ */
+int main(int argc, char **argv)
+{
+    if (argc < 2)
+    {
+        fprintf(stderr, "Usage:...\n");
+        exit(1);
+    }
+
+    char        *input_pass;
+    struct spwd *shadowline;
+    char        *crypt_pass;
+
+    //* getpass()函数在输入密码时不会回显密码
+    input_pass = getpass("PassWord: ");
+
+    //* getspnam()函数通过用户名获取shadow文件中的密码
+    shadowline = getspnam(argv[1]);
+
+    //* 加密输入的密码
+    crypt_pass = crypt(input_pass, shadowline->sp_pwdp);
+
+    if (0 == strcmp(crypt_pass, shadowline->sp_pwdp))
+        puts("OK!");
+    else
+        puts("Error!");
+
+    exit(0);
+}

C14-文件系统/fs/data.csv

@@ -0,0 +1,4 @@
+,语文,数学,英语,总分,评价
+张三,90,91,92,,
+李四,80,81,82,,
+王五,70,71,72,,

C14-文件系统/fs/flen.c

@@ -0,0 +1,41 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+// !!! 不是int
+static off_t flen(char *fname)
+{
+    struct stat statres;
+
+    if (stat(fname, &statres) < 0)
+    {
+        perror("stat()");
+        exit(1);
+    }
+
+    return statres.st_size;
+}
+
+/**
+ * @brief    获取文件大小
+ * @details
+ *           Usage: ./flen filename
+ *
+ * @param    argc
+ * @param    argv
+ * @return  int
+ */
+int main(int argc, char **argv)
+{
+    if (argc < 2)
+    {
+        fprintf(stderr, "Usage:...\n");
+        exit(1);
+    }
+
+    // !!! 通过makefile指定off_t 64位
+    printf("%lld\n", flen(argv[1]));
+
+    exit(0);
+}

C14-文件系统/fs/ftype.c

@@ -0,0 +1,54 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+
+static int ftype(const char *fname)
+{
+    struct stat statres;
+
+    if (stat(fname, &statres) < 0)
+    {
+        perror("stat()");
+        exit(1);
+    }
+
+    if (S_ISREG(statres.st_mode))
+        return '-';
+    else if (S_ISDIR(statres.st_mode))
+        return 'd';
+    else if (S_ISSOCK(statres.st_mode))
+        return 's';
+    else if (S_ISFIFO(statres.st_mode))
+        return 'p';
+    else if (S_ISBLK(statres.st_mode))
+        return 'b';
+    else if (S_ISCHR(statres.st_mode))
+        return 'c';
+    else if (S_ISLNK(statres.st_mode))
+        return 'l';
+    else
+        return '?';
+}
+
+/**
+ * @brief    获取文件类型
+ * @details
+ *           Usage: ftype <filename>
+ *
+ * @param    argc
+ * @param    argv
+ *
+ * @return  int
+ */
+int main(int argc, char **argv)
+{
+    if (argc < 2)
+    {
+        fprintf(stderr, "Usage:...\n");
+        exit(1);
+    }
+
+    printf("%c\n", ftype(argv[1]));
+
+    exit(0);
+}

C14-文件系统/fs/getenv.c

@@ -0,0 +1,17 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+int main(int argc, char **argv)
+{
+
+    puts(getenv("PATH"));
+
+    getchar();
+    /**
+     *  ./getenv
+     *  ps axf | grep getenv
+     *  pmap 4938
+     */
+
+    exit(0);
+}

C14-文件系统/fs/glob.c

@@ -0,0 +1,46 @@
+#include <glob.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+// #define PAT "/etc/a*.conf"
+#define PAT "/etc/*"   // 不包括隐藏文件 .*
+
+#if 0
+static int errfunc_(const char *errpath, int eerrno)
+{
+    puts(errpath);
+    fprintf(stderr, "ERROR MSG: %s\n", strerror(eerrno));
+    return 0;
+}
+#endif
+
+/**
+ * @brief    ls /etc/a*.conf
+ * @details
+ *
+ * @param    argc
+ * @param    argv
+ *
+ * @return  int
+ */
+int main(int argc, char **argv)
+{
+    glob_t globres;
+    int    err;
+
+    err = glob(PAT, 0, NULL, &globres);
+    if (err)
+    {
+        printf("ERROR CODE = %d\n", err);
+        exit(1);
+    }
+
+    for (int i = 0; i < globres.gl_pathc; i++)
+    {
+        puts(globres.gl_pathv[i]);
+    }
+
+    // !!!
+    globfree(&globres);
+    exit(0);
+}

C14-文件系统/fs/jmp.c

@@ -0,0 +1,99 @@
+#include <setjmp.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+static jmp_buf save;
+
+static void d(void)
+{
+    printf("%s():Begin.\n", __FUNCTION__);
+
+    printf("%s():Jump now.\n", __FUNCTION__);
+    longjmp(save, 6);
+    // longjmp(save, 0);   // !!! 如果返回0，实际会返回1，避免与另一种情况冲突
+
+    printf("%s():End.\n", __FUNCTION__);
+}
+
+static void c(void)
+{
+    printf("%s():Begin.\n", __FUNCTION__);
+    printf("%s():Call d().\n", __FUNCTION__);
+
+    d();
+
+    printf("%s():d() returned.\n", __FUNCTION__);
+    printf("%s():End.\n", __FUNCTION__);
+}
+
+static void b(void)
+{
+    printf("%s():Begin.\n", __FUNCTION__);
+    printf("%s():Call c().\n", __FUNCTION__);
+
+    c();
+
+    printf("%s():c() returned.\n", __FUNCTION__);
+    printf("%s():End.\n", __FUNCTION__);
+}
+
+static void a(void)
+{
+    int ret;
+
+    printf("%s():Begin.\n", __FUNCTION__);
+
+    ret = setjmp(save);
+    if (0 == ret)
+    {
+        printf("%s():Call b().\n", __FUNCTION__);
+        b();
+        printf("%s():b() returned.\n", __FUNCTION__);
+    }
+    else
+    {
+        printf("%s():Jumped back here with code %d.\n", __FUNCTION__, ret);
+    }
+
+    printf("%s():End.\n", __FUNCTION__);
+}
+
+
+/**
+ * @brief   jmp
+ * @details
+ *           d跳回a
+ *
+ * @param    argc
+ * @param    argv
+ * @return  int
+ */
+int main(int argc, char **argv)
+{
+    printf("%s():Begin.\n", __FUNCTION__);
+    printf("%s():Call a().\n", __FUNCTION__);
+
+    a();
+
+    printf("%s():a() returned.\n", __FUNCTION__);
+    printf("%s():End.\n", __FUNCTION__);
+
+    exit(0);
+}
+
+
+// ! out
+// main():Begin.
+// main():Call a().
+// a():Begin.
+// a():Call b().
+// b():Begin.
+// b():Call c().
+// c():Begin.
+// c():Call d().
+// d():Begin.
+// d():Jump now.
+// a():Jumped back here with code 6.
+// a():End.
+// main():a() returned.
+// main():End.

C14-文件系统/fs/main.c

@@ -0,0 +1,15 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+int main(int argc, char **argv)
+{
+    printf("argc = %d\n", argc);
+
+    // for (int i = 0; i < argc; i++)
+    for (int i = 0; argv[i] != NULL; i++)
+    {
+        puts(argv[i]);
+    }
+
+    exit(0);
+}

C14-文件系统/fs/main1.c

@@ -0,0 +1,13 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+int main(int argc, char **argv)
+{
+    printf("Hello, World!\n");
+
+    return 0;
+    /*
+     *  echo $?
+     *  0
+     */
+}

C14-文件系统/fs/mydate.c

@@ -0,0 +1,109 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
+
+#define TIMESTRSIZE 1024
+#define FMTSTRSIZE  1024
+
+/**
+ * @brief    mydate
+ * @details
+ *           Usage:
+ *               mydate [-H 12|24] [-y 2|4] [-m] [-d] [-M] [-S]
+ *           Options:
+ *               -y: year 2位,4位
+ *               -m: month
+ *               -d: day
+ *               -H: hour 12小时制,24小时制
+ *               -M: minute
+ *               -S: second
+ *
+ * @param    argc
+ * @param    argv
+ *
+ * @return  int
+ */
+int main(int argc, char **argv)
+{
+    time_t     stamp;
+    struct tm *tm;
+    char       timestr[TIMESTRSIZE];
+    int        c;
+    char       fmtstr[FMTSTRSIZE];
+    fmtstr[0] = '\0';
+    FILE *fp  = stdout;
+
+    time(&stamp);
+    tm = localtime(&stamp);
+
+    while (1)
+    {
+        //* 选项传参
+        // c = getopt(argc, argv, "H:y:MSmd");
+
+        //* 加'-'，接收非选项传参
+        c = getopt(argc, argv, "-H:y:MSmd");
+        if (c < 0)
+            break;
+
+        switch (c)
+        {
+            //* 非选项传参，返回1
+        case 1:
+            if (stdout == fp)   //! 先入为主
+            {
+                fp = fopen(argv[optind - 1], "w");
+                if (NULL == fp)
+                {
+                    perror("fopen()");
+                    fp = stdout;
+                }
+            }
+            break;
+
+        case 'H':
+            if (0 == strcmp(optarg, "12"))
+                strncat(fmtstr, "%I(%P) ", FMTSTRSIZE - 1);
+            else if (0 == strcmp(optarg, "24"))
+                strncat(fmtstr, "%H ", FMTSTRSIZE - 1);
+            else
+                fprintf(stderr,
+                        "Usage: %s [-H 12|24] [-y 2|4] [-m] [-d] [-M] [-S]\n",
+                        argv[0]);
+            break;
+
+        case 'M': strncat(fmtstr, "%M ", FMTSTRSIZE - 1); break;
+
+        case 'S': strncat(fmtstr, "%S ", FMTSTRSIZE - 1); break;
+
+        case 'y':
+            if (0 == strcmp(optarg, "2"))
+                strncat(fmtstr, "%y ", FMTSTRSIZE - 1);
+            else if (0 == strcmp(optarg, "4"))
+                strncat(fmtstr, "%Y ", FMTSTRSIZE - 1);
+            else
+                fprintf(stderr,
+                        "Usage: %s [-H 12|24] [-y 2|4] [-m] [-d] [-M] [-S]\n",
+                        argv[0]);
+            break;
+
+        case 'm': strncat(fmtstr, "%m ", FMTSTRSIZE - 1); break;
+
+        case 'd': strncat(fmtstr, "%d ", FMTSTRSIZE - 1); break;
+
+        default: break;
+        }
+    }
+
+    strncat(fmtstr, "\n", FMTSTRSIZE - 1);
+    strftime(timestr, TIMESTRSIZE, fmtstr, tm);
+
+    fputs(timestr, fp);
+
+    if (fp != stdout)
+        fclose(fp);
+
+    exit(0);
+}

C14-文件系统/fs/mydu.c

@@ -0,0 +1,125 @@
+#include <glob.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#define PATHSIZE 1024
+
+static int path_noloop(const char *path)
+{
+    char *pos;
+
+    /**
+     * @brief    strrchr
+     * @details
+     *
+     *           找到 path 中最后一个 '/' 字符的位置
+     */
+    pos = strrchr(path, '/');
+    if (NULL == pos)
+        exit(1);
+
+    if ((0 == strcmp(pos + 1, ".") || 0 == strcmp(pos + 1, "..")))
+        return 0;
+
+    return 1;
+}
+
+static int64_t mydu(const char *path)
+{
+    // 优化递归
+    // 将部分与递归无关的变量拿出栈，用 static 修饰
+    static struct stat statres;
+    static char        nextpath[PATHSIZE];
+    glob_t             globres;
+    int64_t            sum;
+    int                i;
+
+    if (lstat(path, &statres) < 0)
+    {
+        perror("lstat()");
+        exit(1);
+    }
+
+    if (!S_ISDIR(statres.st_mode))
+    {
+        /* 非目录 */
+        return statres.st_blocks;
+        /*
+         * st_blocks 代表磁盘块数量，一个磁盘块大小为512字节
+         * 所以除以2才表示多少个1k字节
+         */
+    }
+
+    /* 目录 */
+    /* 例如：/aaa/bbb/ccc/ddd/eee/fff */
+
+    strncpy(nextpath, path, PATHSIZE);
+    strncat(nextpath, "/*", PATHSIZE);   //[W]
+    // if (glob(nextpath, 0, NULL, &globres))
+    // {
+    //     perror("glob(), 1");
+    //     exit(1);
+    // }
+    glob(nextpath, 0, NULL, &globres);
+
+    // !!! 要考虑 . 和 .. 目录
+    strncpy(nextpath, path, PATHSIZE);
+    strncat(nextpath, "/.*", PATHSIZE);   //[W]
+    /*
+     * 这个警告是因为 strncat 函数的第三个参数（即 PATHSIZE）等于目标字符串
+     * nextpath 的大小。这可能会导致 nextpath 缓冲区溢出，因为 strncat
+     * 函数会在目标字符串的末尾添加一个 null 字符（'\0'）。
+     */
+
+    // !!! APPEND
+    // if (glob(nextpath, GLOB_APPEND, NULL, &globres))
+    // {
+    //     perror("glob(), APPEND");
+    //     exit(1);
+    // }
+    glob(nextpath, GLOB_APPEND, NULL, &globres);
+
+    sum = statres.st_blocks;
+
+    for (i = 0; i < globres.gl_pathc; i++)
+    {
+        if (path_noloop(globres.gl_pathv[i]))
+        {
+            sum += mydu(globres.gl_pathv[i]);
+        }
+    }
+
+    // !!!
+    globfree(&globres);
+    return sum;
+}
+
+/**
+ * @brief    mydu
+ * @details
+ *           Usage: mydu [FILE]...
+ *
+ *           用到了递归的思想
+ *
+ *           !!! 未考虑权限问题
+ *
+ * @param    argc
+ * @param    argv
+ *
+ * @return  int
+ */
+int main(int argc, char **argv)
+{
+    if (argc < 2)
+    {
+        fprintf(stderr, "Usage: mydu [FILE]...\n");
+        exit(1);
+    }
+
+    printf("%lld\n", mydu(argv[1]) / 2);
+
+    exit(0);
+}

C14-文件系统/fs/myenv.c

@@ -0,0 +1,13 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+extern char **environ;
+
+int main(int argc, char **argv)
+{
+
+    for (int i = 0; environ[i] != NULL; i++)
+        puts(environ[i]);
+
+    exit(0);
+}

C14-文件系统/fs/readdir.c

@@ -0,0 +1,38 @@
+#include <dirent.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+
+#define PAT "/etc"
+
+/**
+ * @brief    解析PAT下文件个数
+ * @details
+ *
+ * @param    argc
+ * @param    argv
+ *
+ * @return  int
+ */
+int main(int argc, char **argv)
+{
+    DIR           *dp;
+    struct dirent *cur;
+
+    dp = opendir(PAT);
+    if (NULL == dp)
+    {
+        perror("opendir()");
+        exit(1);
+    }
+
+    // !!! 注意括号
+    while ((cur = readdir(dp)) != NULL)
+    {
+        puts(cur->d_name);
+    }
+
+    closedir(dp);
+
+    exit(0);
+}

C14-文件系统/fs/result.csv

@@ -0,0 +1,4 @@
+,语文,数学,英语,总分,评价
+张三,90,91,92,273,A+
+李四,80,81,82,243,A
+王五,70,71,72,213,B

C14-文件系统/fs/timelog.c

@@ -0,0 +1,86 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <unistd.h>
+
+#define FNAME   "time.log"
+#define BUFSIZE 1024
+
+/**
+ * @brief    往文件里面输出时间戳
+ * @details
+ *           实例格式：2019-12-12 12:12:12
+ *
+ * @param    argc
+ * @param    argv
+ *
+ * @return  int
+ */
+int main(int argc, char **argv)
+{
+    FILE      *fp;
+    time_t     stamp;
+    struct tm *tm;
+    char       buf[BUFSIZE];
+    int        count = 0;
+
+    fp = fopen(FNAME, "a+");
+    if (fp == NULL)
+    {
+        perror("fopen()");
+        exit(1);
+    }
+
+    while (fgets(buf, BUFSIZE, fp) != NULL)
+        count++;
+
+    while (1)
+    {
+        stamp = time(NULL);
+
+        tm = localtime(&stamp);
+        if (NULL == tm)
+        {
+            perror("localtime()");
+            exit(1);
+        }
+
+        strftime(buf, BUFSIZE, "%Y-%m-%d %H:%M:%S", tm);
+
+        fprintf(fp, "%-4d%s\n", ++count, buf);
+
+        /*
+         *  加了sleep(1)之后就没有输出？
+         *  全缓冲
+         *  因为缓冲区没有满，没有刷新到文件里面
+         */
+        fflush(fp);
+
+        sleep(1);
+    }
+
+    fclose(fp);
+    exit(0);
+}
+
+//! 最终效果
+// *[main][~/Linux-C-Notes/C13-Linux系统编程/fs]$ ./test
+// ^C
+// *[main][~/Linux-C-Notes/C13-Linux系统编程/fs]$ cat time.log
+// 1   2024-05-11 21:53:26
+// 2   2024-05-11 21:53:27
+// 3   2024-05-11 21:53:28
+// 4   2024-05-11 21:53:29
+// 5   2024-05-11 21:53:30
+// *[main][~/Linux-C-Notes/C13-Linux系统编程/fs]$ ./test
+// ^C
+// *[main][~/Linux-C-Notes/C13-Linux系统编程/fs]$ cat time.log
+// 1   2024-05-11 21:53:26
+// 2   2024-05-11 21:53:27
+// 3   2024-05-11 21:53:28
+// 4   2024-05-11 21:53:29
+// 5   2024-05-11 21:53:30
+// 6   2024-05-11 21:53:35
+// 7   2024-05-11 21:53:36
+// 8   2024-05-11 21:53:37
+// 9   2024-05-11 21:53:38

C14-文件系统/fs/username.c

@@ -0,0 +1,29 @@
+#include <pwd.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+/**
+ * @brief    用user id获取用户名
+ * @details
+ *
+ * @param    argc
+ * @param    argv
+ *
+ * @return  int
+ */
+int main(int argc, char **argv)
+{
+    if (argc < 2)
+    {
+        fprintf(stderr, "Usage: %s <user id>\n", argv[0]);
+        exit(1);
+    }
+
+    struct passwd *pwdline;
+
+    pwdline = getpwuid(atoi(argv[1]));
+
+    puts(pwdline->pw_name);
+
+    exit(0);
+}