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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 NEWargv[0]: pgargv[1]: Iargv[2]: amargv[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 & ~umaskO_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