对于Linux系统, 万物皆文件, 包括普通文件, 目录, 设备, 共享库, socket, nfs等

1. 观察vi命令

观察vi /proc/meminfo的文件打开数

• 查询进程ID

  # ps aux |grep meminfo
  root      31542  0.0  0.0 126308  1700 pts/0    T    15:13   0:00 vi /proc/meminfo
  root      31544  0.0  0.0 112648   960 pts/0    S+   15:13   0:00 grep --color=auto meminfo
  

• 根据进程ID, 查看文件打开数

  # lsof -p 31542
  COMMAND   PID USER   FD   TYPE DEVICE  SIZE/OFF      NODE NAME
  vi      31542 root  cwd    DIR  253,0        84 939716632 /opt
  vi      31542 root  rtd    DIR  253,0      4096        64 /
  vi      31542 root  txt    REG  253,0    910040 100666070 /usr/bin/vi
  vi      31542 root  mem    REG  253,0     61752      1261 /usr/lib64/libnss_files-2.17.so
  vi      31542 root  mem    REG  253,0 106070960 100664815 /usr/lib/locale/locale-archive
  vi      31542 root  mem    REG  253,0    143352      1269 /usr/lib64/libpthread-2.17.so
  vi      31542 root  mem    REG  253,0     19888      1558 /usr/lib64/libattr.so.1.1.0
  vi      31542 root  mem    REG  253,0     19344      1249 /usr/lib64/libdl-2.17.so
  vi      31542 root  mem    REG  253,0    398264      1371 /usr/lib64/libpcre.so.1.2.0
  vi      31542 root  mem    REG  253,0   2116736      1243 /usr/lib64/libc-2.17.so
  vi      31542 root  mem    REG  253,0     37056      1561 /usr/lib64/libacl.so.1.1.0
  vi      31542 root  mem    REG  253,0    174520      1355 /usr/lib64/libtinfo.so.5.9
  vi      31542 root  mem    REG  253,0    155744      2991 /usr/lib64/libselinux.so.1
  vi      31542 root  mem    REG  253,0    155064      1236 /usr/lib64/ld-2.17.so
  vi      31542 root    0u   CHR  136,0       0t0         3 /dev/pts/0
  vi      31542 root    1u   CHR  136,0       0t0         3 /dev/pts/0
  vi      31542 root    2u   CHR  136,0       0t0         3 /dev/pts/0
  vi      31542 root    3u   REG  253,0      4096  15191812 /var/tmp/meminfo.swp
  

FD => file description

• cwd = 当前工作目录
• txt = 程序代码
• mem = 内存映射文件, 一般为共享库
• 0=标准输入, 1=标准输出, 2=标准错误, u=读写, r=只读, w=只写

TYPE

• DIR = 目录
• CHR = 字符类型
• REG = 文件

2. proc记录

/proc/31542/fd/目录, 显示vi进程下有4个文件打开数, 剔除了进程本身(包括工作目录, 二进制程序, 共享库等), 只保留操作的目标文件, 所以统计上略有差异

# ll /proc/31542/fd/
total 0
lrwx------ 1 root root 64 Dec  6 15:14 0 -> /dev/pts/0
lrwx------ 1 root root 64 Dec  6 15:14 1 -> /dev/pts/0
lrwx------ 1 root root 64 Dec  6 15:13 2 -> /dev/pts/0
lrwx------ 1 root root 64 Dec  6 15:14 3 -> /var/tmp/meminfo.swp

3. lsof命令

lsof = list open files

3.1. 查看文件相关的进程

# lsof /usr/bin/vi

3.2. 查看用户的文件打开信息

# lsof -u root

3.3. 查看进程的文件打开信息

# lsof -p 31542

3.4. 查看使用监听端口的进程

# lsof  -i:5258
COMMAND      PID USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
docker-pr 129353 root    4u  IPv4 683948      0t0  TCP *:5258 (LISTEN)
docker-pr 129359 root    4u  IPv6 675762      0t0  TCP *:5258 (LISTEN)