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linux下获取一些环境信息的代码

.TP 3
b:\fB PPID\fR \*(EM Parent Process Pid\fR
The process ID of a task's parent.

.TP 3
c:\fB RUSER\fR \*(EM Real User Name\fR
The real user name of the task's owner.

.TP 3
d:\fB UID\fR \*(EM User Id\fR
The effective user ID of the task's owner.

.TP 3
e:\fB USER\fR \*(EM User Name\fR
The effective user name of the task's owner.

.TP 3
f:\fB GROUP\fR \*(EM Group Name\fR
The effective group name of the task's owner.

.TP 3
g:\fB TTY\fR \*(EM Controlling Tty
The name of the controlling terminal.
This is usually the device (serial port, pty, etc.) from which the
process was started, and which it uses for input or output.
However, a task need not be associated with a terminal, in which case
you'll see '?' displayed.

.TP 3
h:\fB PR\fR \*(EM Priority
The priority of the task.

.TP 3
i:\fB NI\fR \*(EM Nice value
The nice value of the task.
A negative nice value means higher priority, whereas a positive nice value
means lower priority.
Zero in this field simply means priority will not be adjusted in determining a
task's dispatchability.

.TP 3
j:\fB P\fR \*(EM Last used \*(PU (SMP)
A number representing the last used processor.
In a true SMP environment this will likely change frequently since the kernel
intentionally uses weak affinity.
Also, the very act of running \*(Me may break this weak affinity and cause more
processes to change \*(PUs more often (because of the extra demand for
\*(Pu time).

.TP 3
k:\fB %CPU\fR \*(EM \*(PU usage
The task's share of the elapsed \*(PU time since the last screen update,
expressed as a percentage of total \*(PU time.
In a true SMP environment, if 'Irix mode' is \*F, \*(Me will operate
in 'Solaris mode' where a task's \*(Pu usage will be divided by the total
number of \*(PUs.
You toggle 'Irix/Solaris' modes with the 'I' \*(CI.

.TP 3
l:\fB TIME\fR \*(EM \*(PU Time
Total \*(PU time the task has used since it started.
When 'Cumulative mode' is \*O, each process is listed with the \*(Pu
time that it and its dead children has used.
You toggle 'Cumulative mode' with 'S', which is a \*(CO and an \*(CI.
\*(XC 'S' \*(CI for additional information regarding this mode.

.TP 3
m:\fB TIME+\fR \*(EM \*(PU Time, hundredths
The same as 'TIME', but reflecting more granularity through hundredths of
a second.

.TP 3
n:\fB %MEM\fR \*(EM Memory usage (RES)
A task's currently used share of available \*(MP.

.TP 3
o:\fB VIRT\fR \*(EM Virtual Image (kb)
The total amount of \*(MV used by the task.
It includes all code, data and shared libraries plus pages that have been
swapped out.

VIRT = SWAP + RES.

.TP 3
p:\fB SWAP\fR \*(EM Swapped size (kb)
The swapped out portion of a task's total \*(MV image.

.TP 3
q:\fB RES\fR \*(EM Resident size (kb)
The non-swapped \*(MP a task has used.

RES = CODE + DATA.

.TP 3
r:\fB CODE\fR \*(EM Code size (kb)
The amount of \*(MP devoted to executable code, also known as
the 'text resident set' size or TRS.

.TP 3
s:\fB DATA\fR \*(EM Data+Stack size (kb)
The amount of \*(MP devoted to other than executable code, also known as
the 'data resident set' size or DRS.

.TP 3
t:\fB SHR\fR \*(EM Shared Mem size (kb)
The amount of \*(MS used by a task.
It simply reflects memory that could be potentially shared with
other processes.

.TP 3
u:\fB nFLT\fR \*(EM Page Fault count
The number of\fB major\fR page faults that have occurred for a task.
A page fault occurs when a process attempts to read from or write to a virtual
page that is not currently present in its address space.
A major page fault is when disk access is involved in making that
page available.

.TP 3
v:\fB nDRT\fR \*(EM Dirty Pages count
The number of pages that have been modified since they were last
written to disk.
Dirty pages must be written to disk before the corresponding physical memory
location can be used for some other virtual page.

.TP 3
w:\fB S\fR \*(EM Process Status
The status of the task which can be one of:
   '\fBD\fR' = uninterruptible sleep
   '\fBR\fR' = running
   '\fBS\fR' = sleeping
   '\fBT\fR' = traced or stopped
   '\fBZ\fR' = zombie

Tasks shown as running should be more properly thought of as 'ready to run'
\*(EM their task_struct is simply represented on the Linux run-queue.
Even without a true SMP machine, you may see numerous tasks in this state
depending on \*(Me's delay interval and nice value.

.TP 3
x:\fB Command\fR \*(EM Command\fB line\fR or Program\fB name\fR
Display the command line used to start a task or the name of the associated
program.
You toggle between command\fI line\fR and\fI name\fR with 'c', which is both
a \*(CO and an \*(CI.

When you've chosen to display command lines, processes without a command
line (like kernel threads) will be shown with only the program name in
parentheses, as in this example:
      \fR( mdrecoveryd )

Either form of display is subject to potential truncation if it's too long to
fit in this field's current width.
That width depends upon other fields selected, their order and the current
screen width.

\*(NT The 'Command' field/column is unique, in that it is not fixed-width.
When displayed, this column will be allocated all remaining screen width (up
to the maximum 512 characters) to provide for the potential growth of program
names into command lines.

.TP 3
y:\fB WCHAN\fR \*(EM Sleeping in Function
Depending on the availability of the kernel link map ('System.map'), this field
will show the name or the address of the kernel function in which the task is
currently sleeping.
Running tasks will display a dash ('-') in this column.

\*(NT By displaying this field, \*(Me's own working set will be increased by
over 700Kb.
Your only means of reducing that overhead will be to stop and restart \*(Me.

.TP 3
z:\fB Flags\fR \*(EM Task Flags
This column represents the task's current scheduling flags which are
expressed in hexadecimal notation and with zeros suppressed.
These flags are officially documented in <linux/sched.h>.
Less formal documentation can also be found on the 'Fields select'
and 'Order fields' screens.

.\" ......................................................................
.SS 2b. SELECTING and ORDERING Columns
.\" ----------------------------------------------------------------------
After pressing the \*(CIs 'f' (Fields select) or \'o' (Order fields) you will
be shown a screen containing the current \fBfields string\fR followed by names
and descriptions for all fields.

Here is a sample\fB fields string\fR from one of \*(Me's four windows/field
groups and an explanation of the conventions used:
.Jbu
Sample fields string:
   \fIANOPQRSTUVXbcdefgjlmyzWHIK\fR
.Jbu
The order of displayed fields corresponds to the order of the letters
in that string.
.Jbu
If the letter is\fI upper case\fR the corresponding field itself will
then be shown as part of the \*(TD (screen width permitting).
This will also be indicated by a leading \*(AS, as in this excerpt:
    \fR...
    \fB* K: %CPU       = CPU usage
    \fR  l: TIME       = CPU Time
    \fR  m: TIME+      = CPU Time, hundredths
    \fB* N: %MEM       = Memory usage (RES)
    \fB* O: VIRT       = Virtual Image (kb)
    \fR...

.TP
.B Fields select\fR screen \*(EM the 'f' \*(CI
You\fI toggle\fR the\fB display\fR of a field by simply pressing the
corresponding letter.

.TP
.B Order fields\fR screen \*(EM the 'o' \*(CI
You\fI move\fR a field to the\fB left\fR by pressing the corresponding\fB
upper case\fR letter and to the\fB right\fR with the\fB lower case\fR
letter.


.\" ----------------------------------------------------------------------
.SH 3. INTERACTIVE Commands
.\" ----------------------------------------------------------------------
Listed below is a brief index of commands within categories.
Some commands appear more than once \*(EM their meaning or scope may vary
depending on the context in which they are issued.

  3a.\fI GLOBAL_Commands\fR
        <Ret/Sp> ?, =, A, B, d, G, h, I, k, q, r, s, W, Z
  3b.\fI SUMMARY_Area_Commands\fR
        l, m, t, 1
  3c.\fI TASK_Area_Commands\fR
        Appearance:  b, x, y, z
        Content:     c, f, H, o, S, u
        Size:        #, i, n
        Sorting:     <, >, F, O, R
  3d.\fI COLOR_Mapping\fR
        <Ret>, a, B, b, H, M, q, S, T, w, z, 0 - 7
  4b.\fI COMMANDS_for_Windows\fR
        -, _, =, +, A, a, G, g, w

.\" ......................................................................
.SS 3a. GLOBAL Commands
The global \*(CIs are\fB always\fR available\fR in both \*(FM and \*(AM.
However, some of these \*(CIs are\fB not available\fR when running
in 'Secure mode'.

If you wish to know in advance whether or not your \*(Me has been secured,
simply ask for help and view the system summary on the second line.

.TP 7
\ \ \<\fBEnter\fR> or <\fBSpace\fR> :\fIRefresh_Display\fR
These commands do nothing, they are simply ignored.
However, they will awaken \*(Me and following receipt of any input
the entire display will be repainted.

Use either of these keys if you have a large delay interval and wish to
see current status,

.TP 7
\ \ \'\fB?\fR\' or \'\fBh\fR\' :\fIHelp\fR
There are two help levels available.
The first will provide a reminder of all the basic \*(CIs.
If \*(Me is\fI secured\fR, that screen will be abbreviated.

Typing 'h' or '?' on that help screen will take you to help for those \*(CIs
applicable to \*(AM.

.TP 7
\ \ \'\fB=\fR\' :\fIExit_Task_Limits\fR
Removes restrictions on which tasks are shown.
This command will reverse any 'i' (idle tasks) and 'n' (max tasks) commands
that might be active.
It also provides for an 'exit' from PID monitoring.
See the '-p' \*(CO for a discussion of PID monitoring.

When operating in \*(AM this command has a slightly broader meaning.

.TP 7
\ \ \'\fBA\fR\' :\fIAlternate_Display_Mode_toggle\fR
This command will switch between \*(FM and \*(AM.
\*(XT 4. ALTERNATE\-DISPLAY Mode and the 'G' \*(CI for insight into
\*(CWs and field groups.

.TP 7
\ \ \'\fBB\fR\' :\fIBold_Disable/Enable_toggle\fR
This command will influence use of the 'bold' terminfo capability and
alters\fB both\fR the \*(SA and \*(TA for the \*(CW.
While it is intended primarily for use with dumb terminals, it can be
applied anytime.

\*(NT When this toggle is \*O and \*(Me is operating in monochrome mode,
the\fB entire display\fR will appear as normal text.
Thus, unless the 'x' and/or 'y' toggles are using reverse for emphasis,
there will be no visual confirmation that they are even on.

.TP 7
*\ \'\fBd\fR\' or \'\fBs\fR\' :\fIChange_Delay_Time_interval\fR
You will be prompted to enter the delay time, in seconds, between
display updates.

Fractional seconds are honored, but a negative number is not allowed.
Entering 0 causes (nearly) continuous updates, with an unsatisfactory
display as the system and tty driver try to keep up with \*(Me's demands.
The delay value is inversely proportional to system loading,
so set it with care.

If at any time you wish to know the current delay time, simply ask for help
and view the system summary on the second line.

.TP 7
\ \ \'\fBG\fR\' :\fIChoose_Another_Window/Field_Group\fR
You will be prompted to enter a number between 1 and 4 designating the
window/field group which should be made the \*(CW.
You will soon grow comfortable with these 4 windows, especially after
experimenting with \*(AM.

.TP 7
\ \ \'\fBI\fR\' :\fIIrix/Solaris_Mode_toggle\fR
When operating in 'Solaris mode' ('I' toggled \*F), a task's \*(Pu usage
will be divided by the total number of \*(PUs.
After issuing this command, you'll be informed of the new state of this toggle.

.TP 7
\ \ \'\fBu\fR\' :\fIselect a user\fR
You will be prompted for a UID or username. Only processes