我正在运行
ls -l | myprogram
基本上我想以正确的方式打印输出。当我们独立ls -l时，可以有很多行。每行包含8个元素。所以我想以ls -l给出输出的方式打印它，但跳过顶部的两个元素（总数）。例如，ls -l给了我们
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
这是我到目前为止。它只是在一行中打印所有元素。 不知道如何在8个元素的行中实现该部分。之后我想比较文件的大小。请帮助，初学者在这里！
答案 0 :(得分：0)
也许你可以找到＆＃34; \ n \ n＆＃34;在您的输入流中，这是空行。从那里，您将获得输入流的其余内容。
答案 1 :(得分：0)
在do while循环中，您可以尝试添加＆＃34; \ n＆＃34;到printf语句，如下所示：
do {
result=scanf("%s",string);
printf("%s\n", string);
} while (result!=EOF);
然而，do / while并不安全 - 请参阅下面的代码。
如果您需要跳过＆＃34;总X＆＃34;你可以用以下两种方式之一做到这一点： 知道它是第一行并跳过它或者进行字符串比较＆＃34;总X＆＃34;然后跳过它。鉴于它会在那里，我可能会选择后一种选择 - 当然，除非很快就会改变。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。
这是一个例子。注意我把它从do / while改为do。这是因为你需要在使用之前检查结果是否= EOF，而上面的do / while并没有给你一个机会去做。一会儿更安全。
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 - 我还没有编译过这个，所以不太确定sizeof（＆＃34; total＆＃34;）在语法上是否正确，但这个想法应该是。
希望这会有所帮助。
答案 2 :(得分：0)
虽然
“ls -l | tail -n +2” 很好的答案。如果你想用你的代码做，只需检查行的开头
...
while (NULL != fgets(string, sizeof(string), stdin)) {
if (strncmp(string, "total", strlen("total")) == 0) {
continue;
}
printf("%s ", string);
}
...
答案 3 :(得分：0)
您可能希望跳过某些与模式匹配的行。使用能够很好地表达正则表达式的语言（例如：awk，perl，ruby，python等）可以做得更好。
您可以读取每一行，但匹配并跳过某些容易检测到模式的行，例如以＆＃34; total＆＃34;开头的行，空行和＆＃34;。＆＃34;和＆＃34; ..＆＃34;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
}
另一种方法是打开目录，读取它并解码文件信息（参见stat（2）），这将跳过＆＃34; total＆＃34;相当方便，
int res;
struct stat statbuf;
char pathname[1024];
DIR* dir;
struct dirent *dp=NULL;
char* fname;
if( !(dir=opendir(dname)) ) {
int ec=errno;
printf("error:-1:cannot opendir %s\n",dname,ec);
return(-1);
}
while ((dp = readdir(dir)) != NULL) {
//printf("file: %s\n",dp->d_name); fflush(stdout);
if( strcmp(dp->d_name,".")==0 ) continue;
if( strcmp(dp->d_name,"..")==0 ) continue;
fname=dp->d_name;
//call stat(2) here on the file,
sprintf(pathname,"%s/%s",dname,dp->d_name);
if( (res=stat(dname, &statbuf)) == -1) {
int ec=errno;
printf("error:-1:cannot stat %s (%d)\n",pathname,ec);
return(-1);
}
//printf("dirwatch:check (%s)\n",pathname);
print_fileinfo(&statbuf,dp->d_name); //left as an exercise for the poster
}
closedir(dir);
您需要解码并打印stat（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