深入理解Android中查看进程(ps)命令

By Long Luo

注:

这篇文章是2013年发表在个人CSDN Blog解析ANDROID ps命令执行后各项参数的含义,今天将其移到个人独立博客站上。

如何查看Android进程信息呢?

可以打开adb shell,然后我们就有2种方法:

1. 直接输入ps命令

输入之后,我们就可以看到如下的信息:

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# ps
ps
USER PID PPID VSIZE RSS WCHAN PC NAME
root 1 0 276 188 c0099f1c 000086e8 S /init
root 2 0 0 0 c004df64 00000000 S kthreadd
root 3 2 0 0 c003fa28 00000000 S ksoftirqd/0
root 4 2 0 0 c004abc0 00000000 S events/0
root 5 2 0 0 c004abc0 00000000 S khelper
root 6 2 0 0 c004abc0 00000000 S suspend
root 7 2 0 0 c004abc0 00000000 S kblockd/0
root 8 2 0 0 c004abc0 00000000 S cqueue
root 9 2 0 0 c01780d0 00000000 S kseriod
root 10 2 0 0 c004abc0 00000000 S kmmcd
root 11 2 0 0 c006efa8 00000000 S pdflush
root 12 2 0 0 c006efa8 00000000 S pdflush
root 13 2 0 0 c0073480 00000000 S kswapd0
root 14 2 0 0 c004abc0 00000000 S aio/0
root 22 2 0 0 c0175900 00000000 S mtdblockdc

那么我们禁不住要问:

USER     PID   PPID  VSIZE  RSS     WCHAN    PC         NAME

那么这些项各代表着什么意思呢?

  1. USER: 进程的当前用户;
  2. PID : 毫无疑问, process ID的缩写,也就进程号;
  3. PPID :process parent ID,父进程ID
  4. VSIZE : virtual size,进程虚拟地址空间大小;
  5. RSS : 进程正在使用的物理内存的大小;
  6. WCHAN :进程如果处于休眠状态的话,在内核中的地址;
  7. PC : program counter,
  8. NAME: process name,进程的名称

Linux ps命令对比:

Android的内核还是Linux的,我们可以和Linux下ps aux命令的各项参数进行对比,可见:

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root@long-desktop:~# ps aux
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 1 0.0 0.2 2804 1684 ? Ss 21:11 0:01 /sbin/init
root 2 0.0 0.0 0 0 ? S 21:11 0:00 [kthreadd]
root 2286 0.0 0.4 8888 3172 ? Ss 21:52 0:00 sshd: root@pts/0
root 2352 0.0 0.2 4684 2048 pts/0 Ss+ 21:52 0:00 -bash
root 2454 0.4 0.4 8888 3164 ? Rs 22:06 0:00 sshd: root@pts/1
root 2518 0.1 0.2 4684 2004 pts/1 Ss 22:06 0:00 -bash
root 2551 0.0 0.1 2736 1088 pts/1 R+ 22:06 0:00 ps aux

在Linux下ps命令各项含义如下所示:

  • %CPU 进程的cpu占用率
  • %MEM 进程的内存占用率
  • VSZ 进程所使用的虚存的大小
  • RSS 进程使用的驻留集大小或者是实际内存的大小
  • TTY 与进程关联的终端(tty)
  • STAT 检查的状态:进程状态使用字符表示的,如R(running正在运行或准备运行)、S(sleeping睡眠)、I(idle空闲)、Z (僵死)、D(不可中断的睡眠,通常是I/O)、P(等待交换页)、W(换出,表示当前页面不在内存)、N(低优先级任务)T(terminate终 止)、W has no resident pages
  • START (进程启动时间和日期)
  • TIME ;(进程使用的总cpu时间)
  • COMMAND (正在执行的命令行命令)
  • NI (nice)优先级
  • PRI 进程优先级编号
  • PPID 父进程的进程ID(parent process id)
  • SID 会话ID(session id)
  • WCHAN 进程正在睡眠的内核函数名称;该函数的名称是从/root/system.map文件中获得的。
  • FLAGS 与进程相关的数字标识

android ps命令实现的源码

android下ps命令的源码的位置:android/system/core/toolbox/ps.c,其实现如下:

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int ps_main(int argc, char **argv)
{

DIR *d;
struct dirent *de;
char *namefilter = 0;
int pidfilter = 0;
int threads = 0;

d = opendir("/proc");
if(d == 0) return -1;

while(argc > 1){
if(!strcmp(argv[1],"-t")) {
threads = 1;
} else if(!strcmp(argv[1],"-x")) {
display_flags |= SHOW_TIME;
} else if(!strcmp(argv[1],"-p")) {
display_flags |= SHOW_PRIO;
} else if(isdigit(argv[1][0])){
pidfilter = atoi(argv[1]);
} else {
namefilter = argv[1];
}
argc--;
argv++;
}

printf("USER PID PPID VSIZE RSS %sWCHAN PC NAME\n",
(display_flags&SHOW_PRIO)?"PRIO NICE RTPRI SCHED ":"");
while((de = readdir(d)) != 0){
if(isdigit(de->d_name[0])){
int pid = atoi(de->d_name);
if(!pidfilter || (pidfilter == pid)) {
ps_line(pid, 0, namefilter);
if(threads) ps_threads(pid, namefilter);
}
}
}
closedir(d);
return 0;
}

我们可以得到每一行数据是如何获得的:

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static int ps_line(int pid, int tid, char *namefilter)
{

char statline[1024];
char cmdline[1024];
char user[32];
struct stat stats;
int fd, r;
char *ptr, *name, *state;
int ppid, tty;
unsigned wchan, rss, vss, eip;
unsigned utime, stime;
int prio, nice, rtprio, sched;
struct passwd *pw;

sprintf(statline, "/proc/%d", pid);
stat(statline, &stats);

if(tid) {
sprintf(statline, "/proc/%d/task/%d/stat", pid, tid);
cmdline[0] = 0;
} else {
sprintf(statline, "/proc/%d/stat", pid);
sprintf(cmdline, "/proc/%d/cmdline", pid);
fd = open(cmdline, O_RDONLY);
if(fd == 0) {
r = 0;
} else {
r = read(fd, cmdline, 1023);
close(fd);
if(r < 0) r = 0;
}
cmdline[r] = 0;
}

fd = open(statline, O_RDONLY);
if(fd == 0) return -1;
r = read(fd, statline, 1023);
close(fd);
if(r < 0) return -1;
statline[r] = 0;

ptr = statline;
nexttok(&ptr); // skip pid
ptr++; // skip "("

name = ptr;
ptr = strrchr(ptr, ')'); // Skip to *last* occurence of ')',
*ptr++ = '\0'; // and null-terminate name.

ptr++; // skip " "
state = nexttok(&ptr);
ppid = atoi(nexttok(&ptr));
nexttok(&ptr); // pgrp
nexttok(&ptr); // sid
tty = atoi(nexttok(&ptr));

nexttok(&ptr); // tpgid
nexttok(&ptr); // flags
nexttok(&ptr); // minflt
nexttok(&ptr); // cminflt
nexttok(&ptr); // majflt
nexttok(&ptr); // cmajflt
#if 1
utime = atoi(nexttok(&ptr));
stime = atoi(nexttok(&ptr));
#else
nexttok(&ptr); // utime
nexttok(&ptr); // stime
#endif
nexttok(&ptr); // cutime
nexttok(&ptr); // cstime
prio = atoi(nexttok(&ptr));
nice = atoi(nexttok(&ptr));
nexttok(&ptr); // threads
nexttok(&ptr); // itrealvalue
nexttok(&ptr); // starttime
vss = strtoul(nexttok(&ptr), 0, 10); // vsize
rss = strtoul(nexttok(&ptr), 0, 10); // rss
nexttok(&ptr); // rlim
nexttok(&ptr); // startcode
nexttok(&ptr); // endcode
nexttok(&ptr); // startstack
nexttok(&ptr); // kstkesp
eip = strtoul(nexttok(&ptr), 0, 10); // kstkeip
nexttok(&ptr); // signal
nexttok(&ptr); // blocked
nexttok(&ptr); // sigignore
nexttok(&ptr); // sigcatch
wchan = strtoul(nexttok(&ptr), 0, 10); // wchan
nexttok(&ptr); // nswap
nexttok(&ptr); // cnswap
nexttok(&ptr); // exit signal
nexttok(&ptr); // processor
rtprio = atoi(nexttok(&ptr)); // rt_priority
sched = atoi(nexttok(&ptr)); // scheduling policy

tty = atoi(nexttok(&ptr));

if(tid != 0) {
ppid = pid;
pid = tid;
}

pw = getpwuid(stats.st_uid);
if(pw == 0) {
sprintf(user,"%d",(int)stats.st_uid);
} else {
strcpy(user,pw->pw_name);
}

if(!namefilter || !strncmp(name, namefilter, strlen(namefilter))) {
printf("%-8s %-5d %-5d %-5d %-5d", user, pid, ppid, vss / 1024, rss * 4);
if(display_flags&SHOW_PRIO)
printf(" %-5d %-5d %-5d %-5d", prio, nice, rtprio, sched);
printf(" %08x %08x %s %s", wchan, eip, state, cmdline[0] ? cmdline : name);
if(display_flags&SHOW_TIME)
printf(" (u:%d, s:%d)", utime, stime);
printf("\n");
}
return 0;
}

进入/proc文件夹

在/proc文件夹下有很多对应进程ID号的子文件夹:

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drwxr-xr-x  23 root       root             4096 2012-10-01 02:09 ../
dr-xr-xr-x 7 root root 0 2013-01-25 21:10 1/
dr-xr-xr-x 7 root root 0 2013-01-25 21:10 10/
dr-xr-xr-x 7 root root 0 2013-01-25 21:11 1001/
dr-xr-xr-x 7 root root 0 2013-01-25 21:11 1076/
dr-xr-xr-x 7 root root 0 2013-01-25 21:10 11/
dr-xr-xr-x 7 root root 0 2013-01-25 21:10 12/
dr-xr-xr-x 7 root root 0 2013-01-25 21:10 13/
dr-xr-xr-x 7 gdm gdm 0 2013-01-25 21:11 1345/
dr-xr-xr-x 7 root root 0 2013-01-25 21:11 1353/
dr-xr-xr-x 7 root root 0 2013-01-25 21:11 1375/
dr-xr-xr-x 7 root root 0 2013-01-25 21:10 14/

我们可以进入对应的文件夹内,可以看到有以下信息,就可以查询到你的进程信息了。

By Long Luo 2016-6-4 02:34:46 ~ 2016-6-4 02:48:18 at Shenzhen, China.