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??cp??????????mycp???

???

?????

mycp???????????

??????

???????????????????????????????

cp?????????????????

• ????????cp /usr/local/src/main.c /root/main.c
• ????????cp /usr/local/src/main.c /root
• ????????cp ?r /usr/local/src /root ??????????sudo cp XX XX????

?????????????

??????C?????C???????????????main????int main(int argc, char* argv[])

argc?????????? argv??????????????

eg1? [root@ubuntu: /root# ./pg I am NEW argv[0]: pg argv[1]: I argv[2]: am argv[3]: NEW

eg2? #include <stdio.h> int main(int argc, char* argv[]){ int i; for (i=0; i<argc; i++){ printf("argv[%d]: %s\n", i, argv[i]); } return 0; }

argv[0]??????? argv[1]~argv[5]??????????????????????????????

????(POSIX API)

???int open(const char *pathname, int oflag, ...) ???????????????????????????? pathname????? oflag???????? O_RDONLY????? O_WRONLY????? O_RDWR?????? O_APPEND?????????? O_CREAT??????????????????????mode??????mode & ~umask O_EXCL???????O_CREAT???????????????????????????????????? O_TRUNC????????????????????????0

????(POSIX API)

???ssize_t read(int filedes, void *buf, size_t nbytes) ????????????? ????

• ?????????????????????????????????????????????????????
• ?????-1???????????????????? ??????????????????????+???????

???(POSIX API)

???ssize_t write(int filedes, const void *buf, size_t nbytes) ????????????? ????

• ????????????
• ?????-1???????????????????? ??????????????????????+???????

????(POSIX API)

???int close(int filedes) ?????????? ????

• ?????0
• ?????-1 ?????????????????????

????(POSIX API)

???off_t lseek(int filedes, off_t offset, int whence) ?????????????? ?????????????????? ????????????????0? ??????O_APPEND??????????????????? ???????????????????????+??????? lseek?????whence?offset?offset????? whence?SEEK_SET???????=???+offset???? whose?SEEK_CUR???????=??????+offset???? whose?SEEK_END???????=???+offset????

????

??POSIX API???????????????????? ??????POSIX???????????????????????????errorno??????????????? extern errorno ????errorno.h

??????????????? ??1?char *strerror(int errnum) ????string.h ????errnum?????????????? ??2?void perror(const char * msg) ????stdio.h ??????msg??????????errorno??????

??? #include <stdio.h> #include <unistd.h> #include <sys/types.h> #include <string.h> #include <errno.h>

extern errorno;

int main(int argc, char *argv[]){ int fd_src, fd_dst; char *buf; int fd_src_length; int n, m;

if (-1 == (fd_src = open(argv[1], O_RONLY))) {
    perror(argv[1]);
    return -1;
}
if (-1 == (fd_dst = open(argv[2], O_WRONLY | O_CREAT | O_TRUNC, 0666))) {
    perror(argv[2]);
    return -1;
}
if (-1 == (fd_src_length = lseek(fd_src, 0, SEEK_END))) {
    exit(-1);
}
buf = (char *)malloc(fd_src_length + 1);
if (buf == NULL) {
    printf("malloc error");
    return -1;
}
memset(buf, '0', fd_src_length + 1);
if ((n = read(fd_src, buf, fd_src_length)) > 0) {
    printf("buf:%d", strlen(buf));
    if (n != (m = write(fd_dst, buf, n))) {
        printf("write error");
        exit(-1);
    }
}
close(fd_src);
close(fd_dst);
free(buf);
return 0;

}

???https://blog.csdn.net/jeff_liu24/article/details/11561401