一、常用用法
有两种常用用法：
1 | ps -o pid -o ppid -o start_time -o s -o tname -o args --sort=start_time,pid -e |
1 | ps -o pid -o ppid -o start_time -o s -o ruser -o rgroup -o euser -o egroup -o tname -o args -p PID |
二、含义与选项
2.1、含义
1、第一种用法的含义
查询所有的进程，需要显示的列有“pid，ppid，start_time，s，tname，args”，先根据“start_time”列升序排序，再根据“pid”列升序排序。
2、第二种用法的含义
根据进程ID（即PID）查询某个进程的详情，需要显示的列有“pid，ppid，start_time，s，ruser，rgroup，euser，egroup，tname，args”。
2.2、选项表示的意思
“-o 列特征码”：表示在最终的结果中显示“列特征码”对应的列。
“–sort 列特征码组合”：表示根据列特征码组合，对最终显示结果进行排序。
“-e”：表示列出所有进程。
“-p PID”：表示只列出进程ID为“PID”的进程。
三、其他
3.1、使用“ps”命令的目标与选择
3.1.1、期望的关于“ps”命令的目标
能够列出所有的进程，只列出自己所选定的几列的信息，能够根据进程创建时间和进程ID升序排序，能够查询已知进程ID对应进程的详细情况。
3.1.2、具体选择
“ps”命令有好几套实现，在具体选择的过程中，要注意使用标准实现方案。
关于“列出所有进程”的标准做法为：ps -e。
关于“只列出自己所选定的几列的信息”的标准做法：[-o keyword]+(表示1到多个这样的组合，其中“keyword”来自于“man ps”页的“STANDARD FORMAT SPECIFIERS”小节)
关于“能够根据进程创建时间和进程ID升序排序”的标准做法：--sort=keyword（“keyword”跟上面一样，同样来自于“man ps”页的“STANDARD FORMAT SPECIFIERS”小节)，如果需要先根据进程创建时间，再根据进程ID升序排序，那么就是“–sort=start_time,pid”。
关于“能够查询已知进程ID对应进程的详细情况”的标准做法：-p PID。
3.2、另外一些概念介绍
3.2.1、什么是“session leaders”
In Linux, every process has several IDs associated with it, including:
- Process ID (PID)
This is an arbitrary number identifying the process. Every process has a unique ID, but after the process exits and the parent process has retrieved the exit status, the process ID is freed to be reused by a new process. - Parent Process ID (PPID)
This is just the PID of the process that started the process in question. - Process Group ID (PGID)
This is just the PID of the process group leader. If PID == PGID, then this process is a process group leader. - Session ID (SID)
This is just the PID of the session leader. If PID == SID, then this process is a session leader.
Sessions and process groups are just ways to treat a number of related processes as a unit. All the members of a process group always belong to the same session, but a session may have multiple process groups.
Normally, a shell will be a session leader, and every pipeline executed by that shell will be a process group. This is to make it easy to kill the children of a shell when it exits. (See exit(3) for the gory details.)
I don’t think there is a special term for a member of a session or process group that isn’t the leader.
3.2.2、进程的“cpu”列信息的含义
cpu utilization of the process in “##.#” format.Currently, it is the CPU time used divided by the time the process has been running(cputime/realtime ratio), expressed as a percentage. It will not add up to 100% unless you are lucky.
3.2.3、进程状态指示符表示的进程状态
Here are the different values that the s output specifiers (header “S”) will display to describe the state of a process:
| 进程状态码 | 含义 |
|---|---|
| D | uninterruptible sleep (usually IO) |
| R | running or runnable (on run queue) |
| S | interruptible sleep (waiting for an event to complete) |
| T | stopped, either by a job control signal or because it is being traced |
| W | paging (not valid since the 2.6.xx kernel) |
| X | dead (should never be seen) |
| Z | defunct (“zombie”) process, terminated but not reaped by its parent |
参考文献
[1]man ps
[2]http://unix.stackexchange.com/questions/18166/what-are-session-leaders-in-ps
