Pstree源码分析

Pstree源码分析
一．getopt_long获取参数，根据参数设置相应的变量。

二．read_proc ()主要函数，获取所有的process,生成tree.
#define PROC_BASE "/proc"
dir =opendir (PROC_BASE))
while ((de = readdir (dir)) != NULL)
if ((pid = (pid_t) atoi (de->d_name)) != 0) //即读取/proc/number
sprintf (path, "%s/%d/stat", PROC_BASE, pid);
//path赋值为/proc/number/stat
if ((file = fopen (path, "r")) != NULL)
sprintf (path, "%s/%d", PROC_BASE, pid); //path赋值为/proc/number
fread(readbuf, 1, BUFSIZ, file) ; //读取/proc/number/stat内容到readbuf
if ((comm = strchr(readbuf, '('))&& (tmpptr = strrchr(comm, ')')))
//comm指向/proc/number/stat第一次出现’(‘的位置
//tmpptr指向/proc/number/stat最后一次出现’)‘的位置
++comm; *tmpptr = 0; //即comm为/proc/number/stat中command内容
if (sscanf(tmpptr+2, "%*c %d", &ppid) == 1)
//从tmpptr+2位置开始的第一个整数指向为ppid
sprintf (taskpath, "%s/task", path);
//taskpath赋值为/proc/number/task
if ((taskdir=opendir(taskpath))!=0)
sprintf(threadname,"{%s}",comm);
// threadname赋值为command
while ((dt = readdir(taskdir)) != NULL)
if ((thread=atoi(dt->d_name)) !=0)
//读取/proc/number/task中的number
if (thread != pid)
//即该number!=pid,也就是该process有子线程
add_proc(threadname, thread, pid, st.st_uid, NULL, 0);
………………..
…………………略
add_proc (comm, pid, ppid, st.st_uid, NULL, 0);
add_proc()函数
add_proc (const char *comm, pid_t pid, pid_t ppid, uid_t uid,
const char *args, int size)
if (!(this = find_proc (pid)))
this = new_proc (comm, pid, uid); //如果没有该process，则生成该pid对应的PROC结构else
{
strcpy (this->comm, comm);
this->uid = uid;
}
if (!(parent = find_proc (ppid)))
parent = new_proc ("?", ppid, 0);
//如果没有该ppid对应的process,则生成ppid对应的PROC结构…………………略
add_child (parent, this);
add_child()函数
add_child (PROC * parent, PROC * child)
CHILD *new, **walk;
new = malloc (sizeof (CHILD))
new->child = child;
for (walk = &parent->children; *walk; walk = &(*walk)->next)
//在该parent对应的children链中循环
if ((cmp = strcmp ((*walk)->child->comm, child->comm)) > 0) break;
else if (!cmp && (*walk)->child->uid > child->uid)
break;
new->next = *walk;
*walk = new;
//在children链中找到合适的位置将该child添加进去
添加规则：
1.按children的command项的字母排序
2.如果command相同，按children的uid从小到大排序
三．dump_tree主要函数，将tree按规则输出
dump_tree (PROC * current, int level, int rep, int leaf, int last, uid_t prev_uid, int closing)
if (!leaf) …………输出一些符号
if(rep>=2) out_string ("*[") //即该PROC不止一个，有重复的for (here = current->comm; *here; here++)
………out_char (*here); ……将该process对应的command输出
if (print_args || !current->children) //该process没有children
…….. ut_char (']');……..
else //该process有children
for (walk = current->children; walk; walk = next)
count = 0;
next = walk->next;
scan = &walk->next;
while (*scan)
if (!tree_equal (walk->child, (*scan)->child))
//如果该child和parent的下一个child形成的tree并不equal
scan = &(*scan)->next;
else //如果tree是equal的
{
if (next == *scan)
next = (*scan)->next;
count++; //count加，即表示该tree有多少
*scan = (*scan)->next;
……..
dump_tree (walk->child, level + 1, count + 1,walk == current->children, !next, current->uid, closing + (count ? 1 : 0));
//递归调用dump_tree，dump该process的children
四．改进
需求：所有由supervise启动的程序，显示程序目录，gpid 。

Pstree在不加user显示的时候，出现
init--2*[supervise---tncache---tncache---35*[tncache]] 两个supervise并成一行
改为分开显示
思路：程序目录：/proc/number/exe符号链接，指向被执行的二进制代码.
gpid : /proc/number/stat获取
判断是否supervise启动：循环parent，找出是否直接或者间接parent的comand 是supervise
分开显示：改变dump_tree的时候，tree_equal的逻辑
将parent是init进程，command是supervise，并且supervise所在的tree是equal 的,按照原来非equal的逻辑处理。