Advanced Programming in the UNIX Environment(4)

Junn9527

                本章学习内容：
1. stat, fstat, and lstat functions
#include
int stat(const char *restrict pathname, struct stat *restrict buf);
int fstat(int filedes, struct stat *buf);
int lstat(const char *restrict pathname, struct stat *restrict buf);
All three ruturn: 0 if OK, -1 on error.
其中：
struct stat {
       mode_t    st_mode;      /* file type & mode (permissions) */
       ino_t     st_ino;       /* i-node number (serial number) */
       dev_t     st_dev;       /* device number (file system) */
       dev_t     st_rdev;      /* device number for special files */
       nlink_t   st_nlink;     /* number of links */
       uid_t     st_uid;       /* user ID of owner */
       gid_t     st_gid;       /* group ID of owner */
       off_t     st_size;      /* size in bytes, for regular files */
       time_t    st_atime;     /* time of last access */
       time_t    st_mtime;     /* time of last modification */
       time_t    st_ctime;     /* time of last file status change */
       blksize_t st_blksize;   /* best I/O block size */
       blkcnt_t  st_blocks;    /* number of disk blocks allocated */
     };
File type macros in :
S_ISREG()——regular file——普通文件；
S_ISDIR()——directory——目录文件；
S_ISCHR()——character special file——字符特殊文件；
S_ISBLK()——block special file——块特殊文件；
S_ISFIFO()——pipe or FIFO——管道或FIFO；
S_ISLNK()——symbolic link——符号连接；
S_ISSOCK()——socket——套接字。
Figure 4.3. Print type of file for each command-line argument
#include "apue.h"
#include
int main(int argc, char *argv[])
{
        int             i;
        struct stat     buf;
        char            *ptr;
        for (i = 1; i
int access(const char *pathname, int mode);
Returns: 0 if OK, -1 on error
The mode constants for access function from
    mode         description
    R_OK        test for read permission
    W_OK        test for write permission   
    X_OK        test for execute permission
    F_OK        test for existence of file

The nine file access permission bits, from
    st_mode mask        meaning
    S_IRUSR            user-read
    S_IWUSR            user-write
    S_IXUSR            user-execute
    S_IRGRP            group-read
    S_IWGRP            group-write
    S_IXGRP            group-execute
    S_IROTH            other-read
    S_IWOTH            other-write
    S_IXOTH            other-execute
figure4.8: access 函数的应用
#include "apue.h"
#include
int main(int argc, char *argv[])
{
        if (argc != 2)
                err_quit("usage: a.out ");
        if (access(argv[1], R_OK)
mode_t umask(mode_t cmask);
Ruturns: previous file mode creation mask
figure4.9. umask 函数的应用
#include "apue.h"
#include
#include
#define RWRWRW (S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH)
int main(void)
{
        umask(0);
        if (creat("foo", RWRWRW)
int chmod(const char *pathname, mode_t mode);
int fchmod(int filedes, mode_t mode);
Both return: 0 if OK, -1 on error
Figure4.12. chmod函数的应用
#include "apue.h"
#include
int main(void)
{
        struct stat             statbuf;
        /* turn on set-group-ID and turn off group-execute */
        if (stat("foo", &statbuf)
int chown(const char *pathname, uid_t owner, gid_t group);
int fchown(int filedes, uid_t owner, gid_t group);
int lchown(const char *pathname, uid_t owner, gid_t group);
All three return: 0 if OK, -1 on error.
6. truncate and ftruncate functions
#include
int truncate(const char *pathname, off_t length);
int ftruncate(int filedes, off_t length);
Both return: 0 if OK, -1 on error.
7. link, unlink, remove and rename functions
#include
int link(const char *existingpath, const char *newpath);
int unlink(const char *pathname);
Both ruturnL: 0 if OK, -1 on error;
#include
int remove(const char *pathname);
int rename(const char *oldname, const char *newname);
Both return: 0 if OK, -1 on error.
Figure 4.16. Open a file and then unlink it
#include "apue.h"
#include
int main(void)
{
        if (open("test", O_RDWR)
int symlink(const char *actualpath const char *sympath);
Returns: 0 if OK, -1 on error;
ssize_t readlink(const char* restrict pathname, char *restrict buf, size_t bufsize);
Returns: number of bytes read if OK, -1 on error.
9. utime function
#inclue
int utime(const char *pathname, const struct utimbuf *times);
Returns: 0 if OKk, -1 on error.
struct utimbuf
{
    time_t acttime;     /* access time */
    time_t modtime;        /* modification time */
}
Figure 4.21. utime函数的应用
#include "apue.h"
#include
#include
#include
int main(int argc, char *argv[])
{
        int             i, fd;
        struct stat     statbuf;
        struct utimbuf  timebuf;
        for (i = 1; i
int mkdir(const char *pathname, mode_t mode);
Returns: 0 if OK, -1 on error;
#include
int rmdir(const char *pathname);
Returns: 0 if OK, -1 on error.
11. reading directories functions
#include
DIR *opendir(const char *pathname);
Returns: pointer if OK, NULL on error
struct dirent *readdir(DIR *dp);
Returns: pointer if OK, NULL at end of directory or error

void rewinddir(DIR *dp);
int closedir(DIR *dp);
Returns: 0 if OK, 1 on error

long telldir(DIR *dp);
Returns: current location in directory associated with dp

void seekdir(DIR *dp, long loc);

struct dirent {
        ino_t d_ino;                  /* i-node number */
        char  d_name[NAME_MAX + 1];   /* null-terminated filename */
      }
Figure 4.22. Recursively descend a directory hierarchy, counting file types
12. chdir, fchdir and getcwd functions
#inclde
int chdir(const char *pathname);
int fchdir(int filedes);
Both return: 0 if OK, -1 on error;
cher *getcwd(char *buf, size_t size);
Return: buf if OK, NULL on error.
Figure 4.23. chdir函数的应用
#include "apue.h"
int main(void)
{
        if (chdir("/tmp")
int main(int argc, char *argv[])
{
        int     i;
        struct stat     buf;
        for (i = 1; i < argc; i++) {
                printf("%s: ", argv);
                if (stat(argv, &buf) < 0) {
                        err_ret("stat error");
                        continue;
                }
                printf("dev = %d/%d", major(buf.st_dev),  minor(buf.st_dev));
                if (S_ISCHR(buf.st_mode) || S_ISBLK(buf.st_mode)) {
                        printf(" (%s) rdev = %d/%d",
                                        (S_ISCHR(buf.st_mode)) ? "character" : "block",
                                        major(buf.st_rdev), minor(buf.st_rdev));
                }
                printf("\n");
        }
        exit(0);
}
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