proc, pflags, pcred, pldd, psig, pstack, pfiles, pwdx, pstop, prun, pwait, ptime - proc tools
/usr/bin/pflags [-r] pid | core [/lwp] ...
/usr/bin/pcred [pid | core]...
/usr/bin/pcred [-u user/uid] [-g group/gid] [-G grouplist] pid...
/usr/bin/pcred -l login pid...
/usr/bin/pldd [-Fl] [pid | core]...
/usr/bin/psig [-n] pid...
/usr/bin/pstack [-F] pid | core [/lwp] ...
/usr/bin/pfiles [-Fn] pid...
/usr/bin/pstop pid[/lwp] ...
/usr/bin/prun pid[/lwp] ...
/usr/bin/pwait [-v] pid...
/usr/bin/ptime command [arg]...
The proc tools are utilities that exercise features of /proc (see proc(4)). Most of them take a list of process-ids (pid). The tools that do take process-ids also accept /proc/nnn as a process-id, so the shell expansion /proc/* can be used to specify all processes in the system.
Some of the proc tools can also be applied to core files (see core(4)). The tools that apply to core files accept a list of either process IDs or names of core files or both.
Some of the proc tools can operate on individual threads. Users can examine only selected threads by appending /thread-id to the process-id or core. Multiple threads can be selected using the - and , delimiters. For example /1,2,7-9 examines threads 1, 2, 7, 8, and 9.
The following general options are supported:
In addition to the general options, pcred supports the following options:
In addition to the general options, pldd supports the following option:
In order to set the credentials of another process, a process must have sufficient privilege to change its user and group ids to those specified according to the rules laid out in setuid(2) and it must have sufficient privilege to control the target process.
These proc tools stop their target processes while inspecting them and reporting the results: pfiles, pldd, and pstack. A process can do nothing while it is stopped. Thus, for example, if the X server is inspected by one of these proc tools running in a window under the X server's control, the whole window system can become deadlocked because the proc tool would be attempting to print its results to a window that cannot be refreshed. Logging in from from another system using rlogin(1) and killing the offending proc tool would clear up the deadlock in this case.
Caution should be exercised when using the -F flag. Imposing two controlling processes on one victim process can lead to chaos. Safety is assured only if the primary controlling process, typically a debugger, has stopped the victim process and the primary controlling process is doing nothing at the moment of application of the proc tool in question.
Some of the proc tools can also be applied to core files, as shown by the synopsis above. A core file is a snapshot of a process's state and is produced by the kernel prior to terminating a process with a signal or by the gcore(1) utility. Some of the proc tools can need to derive the name of the executable corresponding to the process which dumped core or the names of shared libraries associated with the process. These files are needed, for example, to provide symbol table information for pstack(1). If the proc tool in question is unable to locate the needed executable or shared library, some symbol information is unavailable for display. Similarly, if a core file from one operating system release is examined on a different operating system release, the run-time link-editor debugging interface (librtld_db) cannot be able to initialize. In this case, symbol information for shared libraries is not available.
The following exit values are returned:
See attributes(5) for descriptions of the following attributes:
The human readable output is Uncommitted. The options are Committed.
gcore(1), ldd(1), pargs(1), pgrep(1), pkill(1), plimit(1), pmap(1), preap(1), ps(1), ptree(1), ppgsz(1), pwd(1), rlogin(1), time(1), truss(1), wait(1), fcntl(2), fstat(2), setuid(2), dlopen(3C), signal.h(3HEAD), core(4), proc(4), process(4), attributes(5), zones(5)
The following proc tools stop their target processes while inspecting them and reporting the results: pfiles, pldd, and pstack. However, even if pstack operates on an individual thread, it stops the whole process.
A process or thread can do nothing while it is stopped. Stopping a heavily used process or thread in a production environment, even for a short amount of time, can cause severe bottlenecks and even hangs of these processes or threads, causing them to be unavailable to users. Some databases could also terminate abnormally. Thus, for example, a database server under heavy load could hang when one of the database processes or threads is traced using the above mentioned proc tools. Because of this, stopping a UNIX process or thread in a production environment should be avoided.
A process or thread being stopped by these tools can be identified by issuing /usr/bin/ps -eflL and looking for "T" in the first column. Notice that certain processes, for example "sched", can show the "T" status by default most of the time.
The process ID returned for locked files on network file systems might not be meaningful.
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Created 1996-2023 by Maxim Chirkov
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