我正在使用以下命令来获取pipe道列表：
lsof | grep PIPE 我想知道FD列的值是什么意思（第五个http://img.zgserver.com/linux/KHczptf.png ）。 我认为r和w是读和写 ，但是每个字符后面的数字是什么意思？
我知道FD表示文件描述符，我想知道的是什么意思是列中显示的值，如3r，16w，20r等
文件不仅作为流打开。 其中一些被列在lsof手册中：
FD is the File Descriptor number of the file or: cwd current working directory; Lnn library references (AIX); err FD information error (see NAME column); jld jail directory (FreeBSD); ltx shared library text (code and data); Mxx hex memory-mapped type number xx. m86 DOS Merge mapped file; mem memory-mapped file; mmap memory-mapped device; pd parent directory; rtd root directory; tr kernel trace file (OpenBSD); txt program text (code and data); v86 VP/ix mapped file; FD is followed by one of these characters, describing the mode under which the file is open: r for read access; w for write access; u for read and write access; space if mode unknown and no lock character follows; '-' if mode unknown and lock character follows. The mode character is followed by one of these lock charac- ters, describing the type of lock applied to the file: N for a Solaris NFS lock of unknown type; r for read lock on part of the file; R for a read lock on the entire file; w for a write lock on part of the file; W for a write lock on the entire file; u for a read and write lock of any length; U for a lock of unknown type; x for an SCO Openserver Xenix lock on part of the file; X for an SCO Openserver Xenix lock on the entire file; space if there is no lock. See the LOCKS section for more information on the lock information character. The FD column contents constitutes a single field for pars- ing in post-processing scripts.
这是文件描述符 。
更多关于它：
文件描述符 （FD）是访问文件的抽象指示符。 该术语通常用于POSIX操作系统。
在POSIX中，文件描述符是一个整数，特别是C类型的int。 有三个标准的POSIX文件描述符，对应于三个标准流，这大概是每个进程（或许守护进程）应该具有的。