C 正确打印输出

我在做这个

ls -l | myprogram

基本上我想以正确的方式打印输出。当我们单独使用

ls-l

时，可以有许多行。每行包含8个元素。因此，我想以一种方式打印它

ls-l

give output，但跳过顶部的两个元素（总数）。例如，

ls-l

为我们提供

total 3
-rwx------ 1 cre university 8381 Sep 24 21:04 a.out
drwx------ 5 cre university 4096 Sep 16 19:36 file2
-rwx------ 1 cre university 8499 Sep 25 00:50 file1

我需要

ls-l|myprogram

：

-rwx------ 1 cre university 8381 Sep 24 21:04 a.out
drwx------ 5 cre university 4096 Sep 16 19:36 file2
-rwx------ 1 cre university 8499 Sep 25 00:50 file1

这就是我到目前为止所做的。它只需在一行中打印所有元素。

---

当零件与8个元素对齐时，不知道如何实现零件。之后，我想比较文件的大小。请帮助，这里的初学者

您可能可以在输入流中找到“\n\n”，即空行。从那里您将获得输入流的其余内容。

在do while循环中，您可以尝试向printf语句添加“\n”，如下所示：

do {    
    result=scanf("%s",string);
    printf("%s\n", string);
} while (result!=EOF);

但是，do/while不是很安全-请参阅下面的代码

如果需要跳过“总计X”行，可以采用以下两种方法之一： 知道它是第一行并跳过它，或者对“total X”进行字符串比较，然后跳过它。我可能会选择后面的选项，因为它将在那里——当然，除非ls很快改变。为了完全安全，正则表达式可能是最安全的，但实施时间更长

这里有一个例子。注意，我将它从do/while改为do。这是因为在使用之前需要检查result==EOF，而上面的do/while并没有给您这样做的机会。这段时间比较安全

 while (EOF != (result = scanf("%s", string))) {
    // skip line containing "total X"
    if (strncmp(result, "total ", sizeof("total ")) == 0) {
        continue;
    }
    printf("%s\n", string);
 }

免责声明-我还没有编译这个，所以不太确定sizeof（“total”）在语法上是否正确，但这个想法应该是正确的

希望这对你有所帮助

虽然

“ls-l | tail-n+2” 这是个好答案。如果你想用你的代码来做这件事，只需检查行的开头

---

您可能希望跳过某些行，即与模式匹配的行。使用能够很好地处理正则表达式的语言（例如：awk、perl、ruby、python等）可以更好地实现这一点

您可以读取每一行，但可以匹配并跳过某些容易检测到模式的行，例如以“total”开头的行、空行以及“.”和“.”特殊目录

linebuffer[1024];
while( fgets(linbuffer,sizeof(linebuffer),stdin) ) {
    if( strlen(linebuffer) < 2 ) continue; //short lines
    if( strncmp(linebuffer,"total",strlen("total")==0 ) continue; //line begins with "total"
    //do you want to skip ".", ".."?
    if( strcmp(linebuffer+strlen(linebuffer)-2,".\n")==0 ) continue; //skip ".", ".."
    printf("%s",linebuffer); //or use puts
}

您需要解码并打印统计（2）信息

int
print_fileinfo(stat* statbuf, char* name)
{
    //decode rwx bits for owner, group, and other
    //lookup owner and group names
    //file size is part of statbuf
    //file type (regular, directory, et al) is part of statbuf
}

您需要查看stat（2）手册页，但这里有一些有用的值、宏、

   All of these system calls return a stat structure, which contains the following fields:

       struct stat {
           dev_t     st_dev;     /* ID of device containing file */
           ino_t     st_ino;     /* inode number */
           mode_t    st_mode;    /* protection */
           nlink_t   st_nlink;   /* number of hard links */
           uid_t     st_uid;     /* user ID of owner */
           gid_t     st_gid;     /* group ID of owner */
           dev_t     st_rdev;    /* device ID (if special file) */
           off_t     st_size;    /* total size, in bytes */
           blksize_t st_blksize; /* blocksize for file system I/O */
           blkcnt_t  st_blocks;  /* number of 512B blocks allocated */
           time_t    st_atime;   /* time of last access */
           time_t    st_mtime;   /* time of last modification */
           time_t    st_ctime;   /* time of last status change */
       };

   The following POSIX macros are defined to check the file type using the st_mode field:

       S_ISREG(m)  is it a regular file?

       S_ISDIR(m)  directory?

       S_ISCHR(m)  character device?

       S_ISBLK(m)  block device?

       S_ISFIFO(m) FIFO (named pipe)?

       S_ISLNK(m)  symbolic link?  (Not in POSIX.1-1996.)

       S_ISSOCK(m) socket?  (Not in POSIX.1-1996.)

   The following flags are defined for the st_mode field:

       S_IFMT     0170000   bit mask for the file type bit fields
       S_IFSOCK   0140000   socket
       S_IFLNK    0120000   symbolic link
       S_IFREG    0100000   regular file
       S_IFBLK    0060000   block device
       S_IFDIR    0040000   directory
       S_IFCHR    0020000   character device
       S_IFIFO    0010000   FIFO
       S_ISUID    0004000   set UID bit
       S_ISGID    0002000   set-group-ID bit (see below)
       S_ISVTX    0001000   sticky bit (see below)
       S_IRWXU    00700     mask for file owner permissions
       S_IRUSR    00400     owner has read permission
       S_IWUSR    00200     owner has write permission
       S_IXUSR    00100     owner has execute permission
       S_IRWXG    00070     mask for group permissions
       S_IRGRP    00040     group has read permission
       S_IWGRP    00020     group has write permission
       S_IXGRP    00010     group has execute permission
       S_IRWXO    00007     mask for permissions for others (not in group)
       S_IROTH    00004     others have read permission
       S_IWOTH    00002     others have write permission
       S_IXOTH    00001     others have execute permission

---

不是直接回答，但您是否尝试过

ls-l | tail-n+2

？您的预期输出是什么？你不是那样的clear@SukkoPera

sed'1d'

也做同样的事情。然而，在这种情况下，我会投票支持

tail

Sure@starrify，我相信至少还有十几种方法可以做同样的事情：）。

int
print_fileinfo(stat* statbuf, char* name)
{
    //decode rwx bits for owner, group, and other
    //lookup owner and group names
    //file size is part of statbuf
    //file type (regular, directory, et al) is part of statbuf
}

   All of these system calls return a stat structure, which contains the following fields:

       struct stat {
           dev_t     st_dev;     /* ID of device containing file */
           ino_t     st_ino;     /* inode number */
           mode_t    st_mode;    /* protection */
           nlink_t   st_nlink;   /* number of hard links */
           uid_t     st_uid;     /* user ID of owner */
           gid_t     st_gid;     /* group ID of owner */
           dev_t     st_rdev;    /* device ID (if special file) */
           off_t     st_size;    /* total size, in bytes */
           blksize_t st_blksize; /* blocksize for file system I/O */
           blkcnt_t  st_blocks;  /* number of 512B blocks allocated */
           time_t    st_atime;   /* time of last access */
           time_t    st_mtime;   /* time of last modification */
           time_t    st_ctime;   /* time of last status change */
       };

   The following POSIX macros are defined to check the file type using the st_mode field:

       S_ISREG(m)  is it a regular file?

       S_ISDIR(m)  directory?

       S_ISCHR(m)  character device?

       S_ISBLK(m)  block device?

       S_ISFIFO(m) FIFO (named pipe)?

       S_ISLNK(m)  symbolic link?  (Not in POSIX.1-1996.)

       S_ISSOCK(m) socket?  (Not in POSIX.1-1996.)

   The following flags are defined for the st_mode field:

       S_IFMT     0170000   bit mask for the file type bit fields
       S_IFSOCK   0140000   socket
       S_IFLNK    0120000   symbolic link
       S_IFREG    0100000   regular file
       S_IFBLK    0060000   block device
       S_IFDIR    0040000   directory
       S_IFCHR    0020000   character device
       S_IFIFO    0010000   FIFO
       S_ISUID    0004000   set UID bit
       S_ISGID    0002000   set-group-ID bit (see below)
       S_ISVTX    0001000   sticky bit (see below)
       S_IRWXU    00700     mask for file owner permissions
       S_IRUSR    00400     owner has read permission
       S_IWUSR    00200     owner has write permission
       S_IXUSR    00100     owner has execute permission
       S_IRWXG    00070     mask for group permissions
       S_IRGRP    00040     group has read permission
       S_IWGRP    00020     group has write permission
       S_IXGRP    00010     group has execute permission
       S_IRWXO    00007     mask for permissions for others (not in group)
       S_IROTH    00004     others have read permission
       S_IWOTH    00002     others have write permission
       S_IXOTH    00001     others have execute permission