Linux中的proc文件系统
Proc 文件系统 (procfs) 是在系统启动时即时创建并在系统关闭时解散的虚拟文件系统。
它包含有关当前正在运行的进程的有用信息，它被视为内核的控制和信息中心。
proc 文件系统还提供内核空间和用户空间之间的通信媒介。
下面是我电脑上 /proc 的快照。
ls -l /proc
total 0
dr-xr-xr-x 9 root root 0 Mar 31 21:34 1
dr-xr-xr-x 9 root root 0 Mar 31 21:34 10
dr-xr-xr-x 9 avahi avahi 0 Mar 31 21:34 1034
dr-xr-xr-x 9 root root 0 Mar 31 21:34 1036
dr-xr-xr-x 9 root root 0 Mar 31 21:34 1039
dr-xr-xr-x 9 root root 0 Mar 31 21:34 1041
dr-xr-xr-x 9 root root 0 Mar 31 21:34 1043
dr-xr-xr-x 9 root root 0 Mar 31 21:34 1044
dr-xr-xr-x 9 root root 0 Mar 31 21:34 1048
dr-xr-xr-x 9 root root 0 Mar 31 21:34 105
dr-xr-xr-x 9 root root 0 Mar 31 21:34 1078
dr-xr-xr-x 9 root root 0 Mar 31 21:34 11
dr-xr-xr-x 9 root root 0 Mar 31 21:34 1121
dr-xr-xr-x 9 lp lp 0 Mar 31 21:34 1146
dr-xr-xr-x 9 postgres postgres 0 Mar 31 21:34 1149
dr-xr-xr-x 9 mysql mysql 0 Mar 31 21:34 1169
dr-xr-xr-x 9 postgres postgres 0 Mar 31 21:34 1180
dr-xr-xr-x 9 postgres postgres 0 Mar 31 21:34 1181
dr-xr-xr-x 9 postgres postgres 0 Mar 31 21:34 1182
dr-xr-xr-x 9 postgres postgres 0 Mar 31 21:34 1183
dr-xr-xr-x 9 postgres postgres 0 Mar 31 21:34 1184
dr-xr-xr-x 9 root root 0 Mar 31 21:34 1186
dr-xr-xr-x 9 root root 0 Mar 31 21:34 12
...
如果列出目录，您会发现进程的每个 PID 都有一个专用目录。
您只能使用终端在终端上检查目录
ls -l /proc | grep '^d'
现在让我们检查分配PID的特定进程，您可以从ps命令获取任何正在运行的进程的PID
ps -aux
输出：
ps -aux 命令输出
现在检查 PID=7494 突出显示的进程，您可以检查 /proc 文件系统中是否有该进程的条目。
ls -ltr /proc/7494
输出：
total 0
-rw-r--r-- 1 mandeep mandeep 0 Apr 1 01:14 oom_score_adj
dr-xr-xr-x 13 mandeep mandeep 0 Apr 1 01:14 task
-r--r--r-- 1 mandeep mandeep 0 Apr 1 01:16 status
-r--r--r-- 1 mandeep mandeep 0 Apr 1 01:16 stat
-r--r--r-- 1 mandeep mandeep 0 Apr 1 01:16 cmdline
-r--r--r-- 1 mandeep mandeep 0 Apr 1 01:17 wchan
-rw-r--r-- 1 mandeep mandeep 0 Apr 1 01:17 uid_map
-rw-rw-rw- 1 mandeep mandeep 0 Apr 1 01:17 timerslack_ns
-r--r--r-- 1 mandeep mandeep 0 Apr 1 01:17 timers
-r-------- 1 mandeep mandeep 0 Apr 1 01:17 syscall
-r--r--r-- 1 mandeep mandeep 0 Apr 1 01:17 statm
-r-------- 1 mandeep mandeep 0 Apr 1 01:17 stack
-r--r--r-- 1 mandeep mandeep 0 Apr 1 01:17 smaps
-rw-r--r-- 1 mandeep mandeep 0 Apr 1 01:17 setgroups
-r--r--r-- 1 mandeep mandeep 0 Apr 1 01:17 sessionid
-r--r--r-- 1 mandeep mandeep 0 Apr 1 01:17 schedstat
-rw-r--r-- 1 mandeep mandeep 0 Apr 1 01:17 sched
lrwxrwxrwx 1 mandeep mandeep 0 Apr 1 01:17 root -> /proc/2341/fdinfo
-rw-r--r-- 1 mandeep mandeep 0 Apr 1 01:17 projid_map
-r-------- 1 mandeep mandeep 0 Apr 1 01:17 personality
...
在 linux 中，/proc 为每个正在运行的进程包括一个目录，包括内核进程，在名为 /proc/PID 的目录中，这些是存在的目录：
| directory | description |
|---|---|
| /proc/PID/cmdline | Command line arguments. |
| /proc/PID/cpu | Current and last cpu in which it was executed. |
| /proc/PID/cwd | Link to the current working directory. |
| /proc/PID/environ | Values of environment variables. |
| /proc/PID/exe | Link to the executable of this process. |
| /proc/PID/fd | Directory, which contains all file descriptors. |
| /proc/PID/maps | Memory maps to executables and library files. |
| /proc/PID/mem | Memory held by this process. |
| /proc/PID/root | Link to the root directory of this process. |
| /proc/PID/stat | Process status. |
| /proc/PID/statm | Process memory status information. |
| /proc/PID/status | Process status in human readable form. |
/proc 文件系统中的其他一些文件是：
| file | description |
|---|---|
| /proc/crypto | list of available cryptographic modules |
| /proc/diskstats | nformation (including device numbers) for each of the logical disk devices |
| /proc/filesystems | list of the file systems supported by the kernel at the time of listing |
| /proc/kmsg | holding messages output by the kernel |
| /proc/meminfo | summary of how the kernel is managing its memory. |
| /proc/scsi | information about any devices connected via a SCSI or RAID controller |
| /proc/tty | information about the current terminals |
| /proc/version | containing the Linux kernel version, distribution number, gcc version number (used to build the kernel) and any other pertinent information relating to the version of the kernel currently running |
比如/proc/crypto的内容是
less /proc/crypto
name : ccm(aes)
driver : ccm_base(ctr(aes-aesni), cbcmac(aes-aesni))
module : ccm
priority : 300
refcnt : 2
selftest : passed
internal : no
type : aead
async : no
blocksize : 1
ivsize : 16
maxauthsize : 16
geniv :
name : ctr(aes)
driver : ctr(aes-aesni)
module : kernel
priority : 300
refcnt : 3
selftest : passed
internal : no
type : blkcipher
blocksize : 1
min keysize : 16
max keysize : 32
ivsize : 16
geniv : chainiv
...
参考 ：
1) /wiki/Procfs
2) /过程