how do you find the environment for a running p...

So how do you find the environment for a running process? It depends on the OS.

* Solaris
/usr/ucb/ps eww <pid>
or in Solaris 9 and up
pargs -e <pid>
Here, e for environment and ww for extra wide (see `man -s 1b ps'). Note that
with the first command, any user can look at any process before Solaris 9.
Beginning with Solaris 9, or more precisely, Solaris with the relevant security
patch, you can only look at the environment of your own process or if you're
root. Solaris 10 pargs has the same restriction, or security enhancement as Sun
would call it.
See http://sunsolve.sun.com/search/document.do?assetkey=1-26-102215-1
One more way, quite involved though, is by using mdb.
See http://blog.curthread.org/posts/solaris/mdb/display_envp.html
Also see the paragraph labeled IMPORTANT below.

* Linux
ps eww <pid>
cat /proc/<pid>/environ
Must run as process owner or root. The second command returns all strings
jumbled together, which can be piped to a filter to separate:
cat /proc/<pid>/environ | perl -pne '$a=chr(0);s/$a/\n/g'
Also see the paragraph labeled IMPORTANT below.

* Windows
In Process Explorer (available from sysinternals.com), double click the
process, go to Environment tab. If the string is too long, you can highlight
and copy and paste into Notepad.

* Other OSes
All BSD's and BSD "derivatives" accept `ps eww <pid>' command. Failing that,
see if you have gdb installed. If so, `gdb path_to_process_executable <pid>'
and enter:
set variable $p = (char **)environ
while *$p
print *$p++
end
(Note that gdb `show environment' does NOT show the attached process
environment.) Without gdb, create a process core image, run strings on the core
file, and find the environment variables usually toward the end of the output
(possibly not very readable). gcore is available on most UNIXes. If not, send
to the process a signal whose disposition is dumping core.

********** IMPORTANT **********
On UNIX and Linux, what I call running process environment is not technically
accurate. It's really the environment at the time the process was created
(fork() and exec()). If the process later changes its environment variables
(create, unset, change value), the above method won't detect the change. (On
Solaris, even the mdb method won't help.) Windows does not suffer from this
problem.
********** IMPORTANT **********

If you see incorrect environment setting, correct it by referring to the
documentation of the application software. If the documentation has no such
information, the general solution is to start the process from a shell or batch
file where the correct environment is pre-set. Suppose a UNIX or Linux process
XYZ has $PATH set to mistakenly include /usr/ccs. Simply type
export PATH=<desired path without /usr/ccs>
XYZ
to launch the application
Sometimes the problem is that you can't start XYZ and the solution is the same.

That sounds trivial to a UNIX/Linux user, but may not be so to a Windows user.
Most Windows programs are started from Start | Programs | ... How do you
control the environment? It's the same answer. When you navigate to the program
from Start | Programs | ..., right click to go to Properties | Shortcut (second
tab), use the long strings in Target and also "Start in" (if not empty) to
manually start the program. Go to DOS (Start | Run | cmd | OK). Type
cd /d <"Start in" from above>
set <envvar>=<desired value>
<"Target" string>
Here <envvar> is the environment variable you wish to change. Make sure there's
no space around "=". Many times I have to manually change %PATH% to make it
much cleaner as in this example:
set path=c:\windows\system32;c:\Program Files\Oracle\jre\1.3.1\bin
Sometimes I explicitly set %TNS_ADMIN% to some path I want to troubleshoot
Oracle TNS connection problem. One practical example of solving a problem this
way is in section "Can't launch Net Manager and Config Assistant" of
http://yong321.freeshell.org/oranotes/LdapInsteadOfTnsnames.txt

For Windows NT Users: To find the "Start in" and Target for a shortcut in
Start | Programs | ..., navigate to C: | Winnt (%SYSTEMROOT%) | Profiles |
<user you, or All Users> | Start Menu | Programs | ... | Properties.

Obviously, you can put the three DOS commands I listed above in a batch file
(XYZ.bat, e.g.) in order to save typing next time. You can also change the
environment setting in Control Panel | System. But the approach outlined here
avoids globally changing the environment which other programs unfamiliar to you
may rely on.

Note that although a messed-up path is a common cause of application problems,
it's not the only one. Even for paths, the environment variable to correct may
not be $PATH on UNIX/Linux; it may be $LD_LIBRARY_PATH or $SHLIB_PATH,
$CLASSPATH, or even without the word "PATH" such as $LD_PRELOAD. On Windows,
however, DLLs are searched in the order of %PATH%, just like EXE files; Windows
has no $LD_LIBRARY_PATH equivalent.

Windows has one more complication and this probably explains some of the
mysteries that sometimes only a reboot can solve a problem. The above method
only works for interactive processes. Windows services are a very different
type of processes. Even if you change the starting shell environment, or the
setting from Control Panel | System | Advanced | Environment Variables, a
stopped and restarted service still uses the old environment. Let's say you
notice that Microsoft SQL Server jobs are failing and Process Explorer shows
that the SQLAgent.exe process seems to have incorrect %PATH%. You also find
that you can execute a DTS task interactively (not by scheduling a job) if you
take the above approach (run mmc.exe /c ... in a clean %PATH% DOS shell) but
fail without cleaning up the shell.  The problem with the restarted service
even after Environment Variables are changed in Control Panel is that a service
is always a child of SERVICES.EXE, which is a child of WINLOGON.EXE, which is a
child of SMSS.EXE, which is a child of System. (NT doesn't have SMSS.EXE) None
of these processes can be killed without crashing the server. SERVICES.EXE uses
all environment variables set in Control Panel. Since these processes exist and
never exit since server bootup, they still take the old environment setting
after you change it in Control Panel. The only way to change their running
process environment (for individual services to inherit) is by reboot after you
properly set it in Control Panel.

转载于:https://my.oschina.net/huxuanhui/blog/42779

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