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Test Your Knowledge in Computers #552
Difficulty: Medium
If variable i has the value 10, after x = 5 + (++i); the value of x after this code is 15.
True or False?
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ps(1) [opendarwin man page]

PS(1)							    BSD General Commands Manual 						     PS(1)

NAME
ps -- process status SYNOPSIS
ps [-aCcefhjlMmrSTuvwx] [-O fmt] [-o fmt] [-p pid] [-t tty] [-U username] ps [-L] DESCRIPTION
Ps displays a header line followed by lines containing information about your processes that have controlling terminals. This information is sorted by controlling terminal, then by process ID. The information displayed is selected based on a set of keywords (see the -L -O and -o options). The default output format includes, for each process, the process' ID, controlling terminal, cpu time (including both user and system time), state, and associated command. The process file system (see procfs(5) ) should be mounted when ps is executed, otherwise not all information will be available. The options are as follows: -a Display information about other users' processes as well as your own. -c Change the ``command'' column output to just contain the executable name, rather than the full command line. -C Change the way the cpu percentage is calculated by using a ``raw'' cpu calculation that ignores ``resident'' time (this normally has no effect). -e Display the environment as well. -f Show commandline and environment information about swapped out processes. This option is honored only if the uid of the user is 0. -h Repeat the information header as often as necessary to guarantee one header per page of information. -j Print information associated with the following keywords: user, pid, ppid, pgid, sess, jobc, state, tt, time and command. -L List the set of available keywords. -l Display information associated with the following keywords: uid, pid, ppid, cpu, pri, nice, vsz, rss, wchan, state, tt, time and com- mand. -M Print the threads corresponding to each task. -m Sort by memory usage, instead of by process ID. -O Add the information associated with the space or comma separated list of keywords specified, after the process ID, in the default information display. Keywords may be appended with an equals (``='') sign and a string. This causes the printed header to use the specified string instead of the standard header. -o Display information associated with the space or comma separated list of keywords specified. Keywords may be appended with an equals (``='') sign and a string. This causes the printed header to use the specified string instead of the standard header. -p Display information associated with the specified process ID. -r Sort by current cpu usage, instead of by process ID. -S Change the way the process time is calculated by summing all exited children to their parent process. -T Display information about processes attached to the device associated with the standard input. -t Display information about processes attached to the specified terminal device. -U Display the processes belonging to the specified username. -u Display information associated with the following keywords: user, pid, %cpu, %mem, vsz, rss, tt, state, start, time and command. The -u option implies the -r option. -v Display information associated with the following keywords: pid, state, time, sl, re, pagein, vsz, rss, lim, tsiz, %cpu, %mem and command. The -v option implies the -m option. -w Use 132 columns to display information, instead of the default which is your window size. If the -w option is specified more than once, ps will use as many columns as necessary without regard for your window size. -x Display information about processes without controlling terminals. A complete list of the available keywords are listed below. Some of these keywords are further specified as follows: %cpu The cpu utilization of the process; this is a decaying average over up to a minute of previous (real) time. Since the time base over which this is computed varies (since processes may be very young) it is possible for the sum of all %CPU fields to exceed 100%. %mem The percentage of real memory used by this process. flags The flags associated with the process as in the include file <sys/proc.h>: P_ADVLOCK 0x00001 Process may hold a POSIX advisory lock P_CONTROLT 0x00002 Has a controlling terminal P_INMEM 0x00004 Loaded into memory P_NOCLDSTOP 0x00008 No SIGCHLD when children stop P_PPWAIT 0x00010 Parent is waiting for child to exec/exit P_PROFIL 0x00020 Has started profiling P_SELECT 0x00040 Selecting; wakeup/waiting danger P_SINTR 0x00080 Sleep is interruptible P_SUGID 0x00100 Had set id privileges since last exec P_SYSTEM 0x00200 System proc: no sigs, stats or swapping P_TIMEOUT 0x00400 Timing out during sleep P_TRACED 0x00800 Debugged process being traced P_WAITED 0x01000 Debugging process has waited for child P_WEXIT 0x02000 Working on exiting P_EXEC 0x04000 Process called exec P_NOSWAP 0x08000 Another flag to prevent swap out P_PHYSIO 0x10000 Doing physical I/O P_OWEUPC 0x20000 Owe process an addupc() call at next ast P_SWAPPING 0x40000 Process is being swapped lim The soft limit on memory used, specified via a call to setrlimit(2). lstart The exact time the command started, using the ``%c'' format described in strftime(3). nice The process scheduling increment (see setpriority(2)). rss the real memory (resident set) size of the process (in 1024 byte units). start The time the command started. If the command started less than 24 hours ago, the start time is displayed using the ``%l:ps.1p'' for- mat described in strftime(3). If the command started less than 7 days ago, the start time is displayed using the ``%a6.15p'' format. Otherwise, the start time is displayed using the ``%e%b%y'' format. state The state is given by a sequence of letters, for example, ``RWNA''. The first letter indicates the run state of the process: D Marks a process in disk (or other short term, uninterruptible) wait. I Marks a process that is idle (sleeping for longer than about 20 seconds). R Marks a runnable process. S Marks a process that is sleeping for less than about 20 seconds. T Marks a stopped process. Z Marks a dead process (a ``zombie''). Additional characters after these, if any, indicate additional state information: + The process is in the foreground process group of its control terminal. < The process has raised CPU scheduling priority. > The process has specified a soft limit on memory requirements and is currently exceeding that limit; such a process is (nec- essarily) not swapped. A the process has asked for random page replacement (VA_ANOM, from vadvise(2), for example, lisp(1) in a garbage collect). E The process is trying to exit. L The process has pages locked in core (for example, for raw I/O). N The process has reduced CPU scheduling priority (see setpriority(2)). S The process has asked for FIFO page replacement (VA_SEQL, from vadvise(2), for example, a large image processing program using virtual memory to sequentially address voluminous data). s The process is a session leader. V The process is suspended during a vfork. W The process is swapped out. X The process is being traced or debugged. tt An abbreviation for the pathname of the controlling terminal, if any. The abbreviation consists of the three letters following /dev/tty, or, for the console, ``con''. This is followed by a ``-'' if the process can no longer reach that controlling terminal (i.e., it has been revoked). wchan The event (an address in the system) on which a process waits. When printed numerically, the initial part of the address is trimmed off and the result is printed in hex, for example, 0x80324000 prints as 324000. When printing using the command keyword, a process that has exited and has a parent that has not yet waited for the process (in other words, a zombie) is listed as ``<defunct>'', and a process which is blocked while trying to exit is listed as ``<exiting>''. Ps makes an educated guess as to the file name and arguments given when the process was created by examining memory or the swap area. The method is inherently somewhat unreliable and in any event a process is entitled to destroy this information, so the names cannot be depended on too much. The ucomm (accounting) keyword can, however, be depended on. KEYWORDS
The following is a complete list of the available keywords and their meanings. Several of them have aliases (keywords which are synonyms). %cpu percentage cpu usage (alias pcpu) %mem percentage memory usage (alias pmem) acflag accounting flag (alias acflg) command command and arguments cpu short-term cpu usage factor (for scheduling) flags the process flags, in hexadecimal (alias f) gid the effective gid inblk total blocks read (alias inblock) jobc job control count ktrace tracing flags ktracep tracing vnode lim memoryuse limit logname login name of user who started the process lstart time started majflt total page faults minflt total page reclaims msgrcv total messages received (reads from pipes/sockets) msgsnd total messages sent (writes on pipes/sockets) nice nice value (alias ni) nivcsw total involuntary context switches nsigs total signals taken (alias nsignals) nswap total swaps in/out nvcsw total voluntary context switches nwchan wait channel (as an address) oublk total blocks written (alias oublock) p_ru resource usage (valid only for zombie) paddr swap address pagein pageins (same as majflt) pgid process group number pid process ID poip pageouts in progress ppid parent process ID pri scheduling priority re core residency time (in seconds; 127 = infinity) rgid real group ID rlink reverse link on run queue, or 0 rss resident set size rsz resident set size + (text size / text use count) (alias rssize) rtprio realtime priority (101 = not a realtime process) ruid real user ID ruser user name (from ruid) sess session pointer sig pending signals (alias pending) sigcatch caught signals (alias caught) sigignore ignored signals (alias ignored) sigmask blocked signals (alias blocked) sl sleep time (in seconds; 127 = infinity) start time started state symbolic process state (alias stat) svgid saved gid from a setgid executable svuid saved uid from a setuid executable tdev control terminal device number time accumulated cpu time, user + system (alias cputime) tpgid control terminal process group ID tsess control terminal session pointer tsiz text size (in Kbytes) tt control terminal name (two letter abbreviation) tty full name of control terminal uprocp process pointer ucomm name to be used for accounting uid effective user ID upr scheduling priority on return from system call (alias usrpri) user user name (from uid) vsz virtual size in Kbytes (alias vsize) wchan wait channel (as a symbolic name) xstat exit or stop status (valid only for stopped or zombie process) FILES
/dev special files and device names /var/run/dev.db /dev name database /var/db/kvm_kernel.db system namelist database /proc the mount point of procfs(5) SEE ALSO
kill(1), w(1), kvm(3), strftime(3), procfs(5), pstat(8) BUGS
Since ps cannot run faster than the system and is run as any other scheduled process, the information it displays can never be exact. 4th Berkeley Distribution April 18, 1994 4th Berkeley Distribution

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