文件和目录

#include <sys/types.h>
#include <fcntl.h>
#include "apue.h"

int main(int argc, char *argv[]) 
{
    if(argc != 2) 
        err_quit("usage: a.out <pathname>"); 

    if(access(argv[1], R_OK) < 0) 
        err_ret("access error for %s", argv[1]); 
    else 
        printf("read access OK\n");

    if(open(argv[1], O_RDONLY) < 0) 
        err_ret("open error for %s", argv[1]); 
    else 
        printf("open for reading OK\n");

    exit(0);
}

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include "apue.h"

int main(void)
{
    umask(0); //foo的权限是666
    if(creat("foo", S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH) < 0)
        err_sys("creat error for foo");

    umask(S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH);
    //bar的权限是600
    if(creat("bar", S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH) < 0)
        err_sys("creat error for bar");

    exit(0);

}

#include <sys/types.h>
#include <sys/stat.h>
#include "apue.h"

int main(void)
{
    struct stat statbuf;

    if(stat("foo", &statbuf) < 0)
        err_sys("stat error for foo");

    /* turn on set-group-ID and turn off group-execute */
    if(chmod("foo", (statbuf.st_mode & ~S_IXGRP) | S_ISGID) < 0)
        err_sys("chmod error for foo");

    /*set absolute mode to "rw-r--r--"*/
    if(chmod("bar", S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH) < 0)
        err_sys("chmod error for bar");

    exit(0);

}

$ mkdir testdir

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include "apue.h"

int main(void)
{
    if(open("tempfile", O_RDWR) < 0)
        err_sys("open error");

    if(unlink("tempfile") < 0)
        err_sys("unlink error");
    printf("file unlinked\n");

    sleep(15);
    printf("done\n");

    exit(0);

}

$ echo "hello world " > tempfile

$ ls -l tempfile
# 1表示有1个目录项目指向tempfile
-rw-r--r-- 1 klose klose 13 Jan 30 22:53 tempfile

$ ./unlinkExample

file unlinked
done

$ ls -l tempfile

ls: cannot access 'tempfile': No such file or directory

$mkdir foo #创建一个新目录

$touch foo/a #创建0长文件

$ln - s ../foo foo/testdir #创建一符号连接

$ls -1 foo

total 1
-rw-rw-r-- 1 stevens 0 Dec6 06:06 a
lrwxrwxrwx 1 stevens 6 Dec6 06:06 testdir -> ../foo

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <utime.h>
#include "apue.h"

int main(int argc, char *argv[])
{
    int i;
    struct stat statbuf;
    struct utimbuf timebuf;

    for(i = 1; i < argc ; ++i) {
        if(stat(argv[i], &statbuf) < 0) {
            err_ret("%s: stat error", argv[i]);
            continue;
        }

        if(open(argv[i], O_RDWR | O_TRUNC) < 0) {
            err_ret("%s: open error", argv[i]);
            continue;
        }

        timebuf.actime = statbuf.st_atime;
        timebuf.modtime = statbuf.st_mtime;
        if(utime(argv[i], &timebuf)< 0) {
            err_ret("%s: utime error", argv[i]);
            continue;
        }
    }

    exit(0);    
}

$ls -l helloworld
-rw-r--r-- 1 klose klose 12 Jan 31 22:42 helloworld

$ls -lu helloworld
-rw-r--r-- 1 klose klose 12 Jan 31 22:42 helloworld

$./utimeExample helloworld

$ls -l helloworld
-rw-r--r-- 1 klose klose 0 Jan 31 22:42 helloworld

$ls -lu helloworld
-rw-r--r-- 1 klose klose 0 Jan 31 22:42 helloworld

#include "apue.h"
#include <dirent.h>
#include <limits.h>

/* function type that is called for each filename */
typedef int Myfunc(const char *, const struct stat *, int);

static Myfunc   myfunc;
static int      myftw(char *, Myfunc *);
static int      dopath(Myfunc *);

static long nreg, ndir, nblk, nchr, nfifo, nslink, nsock, ntot;

/*
 * Descend through the hierarchy, starting at "pathname".
 * The caller's func() is called for every file.
 */
#define FTW_F   1       /* file other than directory */
#define FTW_D   2       /* directory */
#define FTW_DNR 3       /* directory that can't be read */
#define FTW_NS  4       /* file that we can't stat */

static char *fullpath;      /* contains full pathname for every file */

/*
 * Descend through the hierarchy, starting at "fullpath".
 * If "fullpath" is anything other than a directory, we lstat() it,
 * call func(), and return.  For a directory, we call ourself
 * recursively for each name in the directory.
 */
static int dopath(Myfunc* func)  /* we return whatever func() returns */
{
    struct stat     statbuf;
    struct dirent   *dirp;
    DIR             *dp;
    int             ret;
    char            *ptr;

    if (lstat(fullpath, &statbuf) < 0)  /* stat error */
        return(func(fullpath, &statbuf, FTW_NS));
    if (S_ISDIR(statbuf.st_mode) == 0)  /* not a directory */
        return(func(fullpath, &statbuf, FTW_F));

    /*
     * It's a directory.  First call func() for the directory,
     * then process each filename in the directory.
     */
    if ((ret = func(fullpath, &statbuf, FTW_D)) != 0)
        return(ret);

    ptr = fullpath + strlen(fullpath);  /* point to end of fullpath */
    *ptr++ = '/';
    *ptr = 0;

    if ((dp = opendir(fullpath)) == NULL)   /* can't read directory */
        return(func(fullpath, &statbuf, FTW_DNR));

    while ((dirp = readdir(dp)) != NULL) {
        if (strcmp(dirp->d_name, ".") == 0  ||
            strcmp(dirp->d_name, "..") == 0)
            continue;       /* ignore dot and dot-dot */

        strcpy(ptr, dirp->d_name);  /* append name after slash */

        if ((ret = dopath(func)) != 0)      /* recursive */
            break;  /* time to leave */
    }
    ptr[-1] = 0;    /* erase everything from slash onwards */

    if (closedir(dp) < 0)
        err_ret("can't close directory %s", fullpath);

    return(ret);
}

static int myfunc(const char *pathname, const struct stat *statptr, int type)
{
    switch (type) {
    case FTW_F:
        switch (statptr->st_mode & S_IFMT) {
        case S_IFREG:   nreg++;     break;
        case S_IFBLK:   nblk++;     break;
        case S_IFCHR:   nchr++;     break;
        case S_IFIFO:   nfifo++;    break;
        case S_IFLNK:   nslink++;   break;
        case S_IFSOCK:  nsock++;    break;
        case S_IFDIR:
            err_dump("for S_IFDIR for %s", pathname);
            /* directories should have type = FTW_D */
        }
        break;

    case FTW_D:
        ndir++;
        break;

    case FTW_DNR:
        err_ret("can't read directory %s", pathname);
        break;

    case FTW_NS:
        err_ret("stat error for %s", pathname);
        break;

    default:
        err_dump("unknown type %d for pathname %s", type, pathname);
    }

    return(0);
}

/* we return whatever func() returns */
static int myftw(char *pathname, Myfunc *func)
{
    int len;
    fullpath = path_alloc(&len);    /* malloc's for PATH_MAX+1 bytes */
    strncpy(fullpath, pathname, len);   /* protect against */
    fullpath[len-1] = 0;                /* buffer overrun */

    return(dopath(func));
}

int main(int argc, char *argv[])
{
    int     ret;

    if (argc != 2)
        err_quit("usage:  ftw  <starting-pathname>");

    ret = myftw(argv[1], myfunc);       /* does it all */

    ntot = nreg + ndir + nblk + nchr + nfifo + nslink + nsock;
    if (ntot == 0)
        ntot = 1;       /* avoid divide by 0; print 0 for all counts */
    printf("regular files  = %7ld, %5.2f %%\n", nreg,
           nreg*100.0/ntot);
    printf("directories    = %7ld, %5.2f %%\n", ndir,
           ndir*100.0/ntot);
    printf("block special  = %7ld, %5.2f %%\n", nblk,
           nblk*100.0/ntot);
    printf("char special   = %7ld, %5.2f %%\n", nchr,
           nchr*100.0/ntot);
    printf("FIFOs          = %7ld, %5.2f %%\n", nfifo,
           nfifo*100.0/ntot);
    printf("symbolic links = %7ld, %5.2f %%\n", nslink,
           nslink*100.0/ntot);
    printf("sockets        = %7ld, %5.2f %%\n", nsock,
           nsock*100.0/ntot);

    exit(ret);
}

#include "apue.h"

int main(void)
{
    if (chdir("/tmp") < 0)
        err_sys("chdir failed");
    printf("chdir to /tmp succeeded\n");
    exit(0);
}

$ pwd
/home/klose/Documents/programming/c/apue

$ ./src/file_directory/chdirExample
chdir to /tmp succeeded

$ pwd
/home/klose/Documents/programming/c/apue

#include "apue.h"

int main(void)
{
    char    *ptr;
    int     size;

    if (chdir("/home/klose/Applications/maven/") < 0)
        err_sys("chdir failed");

    ptr = path_alloc(&size);    /* our own function */
    if (getcwd(ptr, size) == NULL)
        err_sys("getcwd failed");

    printf("cwd = %s\n", ptr);
    exit(0);
}

$ pwd
/home/klose/Documents/programming/c/apue

$ ./src/file_directory/getpwdExample 
cwd = /home/klose/Applications/apache-maven-3.3.9