246

I need to troubleshoot some problems related to environment variables on a Unix system.

On Windows, I can use a tool such as ProcessExplorer to select particular a process and view values of each environment variable.

How can I accomplish the same thing on Unix? echoing and env cmd just show values at present time, but I want to view what values the running process is using currently.

Desperatuss0ccus
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Gant
  • 2,605

13 Answers13

317
cat /proc/<pid>/environ

If you want to have pid(s) of a given running executable you can, among a number of other possibilities, use pidof. Example:

pidof sshd   
30690 6512

EDIT:

I totally quote Dennis Williamson and Teddy comments to achieve a more readable output. My solution is the following:

tr '\0' '\n' < /proc/<pid>/environ
Patrizio Bertoni
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  • 3
drAlberT
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64

Since this question has a unix tag and everyone else has done such a great job addressing linux tag, you can get this information on OS X and other BSD-derived systems using

ps -p <PID> -wwwe

or

ps -p <PID> -wwwE

and on Solaris with

/usr/ucb/ps -wwwe <PID>

Solaris also supports the /proc directory if you don't want to remember the obscure ps commmand.

Mark Stewart
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Gerald Combs
  • 6,591
26

As others have mentioned, on Linux, you can look in /proc but there are, depending on your kernel version, one or two limits:

First of all, the environ file contains the environment as it looked when the process was spawned. That means that any changes the process might have made to its environment will not be visible in /proc:

$ cat /proc/$$/environ | wc -c
320
$ bash
$ cat /proc/$$/environ | wc -c
1270
$

The first shell is a login shell and initially has a very limited environment but grows it by sourcing e.g. .bashrc but /proc does not reflect this. The second shell inherits the larger environment from the start, which it why it shows in /proc.

Also, on older kernels, the contents of the environ file is limited to a page size (4K):

$ cat /proc/$$/environ | wc -c
4096
$ env | wc -c
10343
$

Somewhere between 2.6.9 (RHEL4) and 2.6.18 (RHEL5) this limit was removed...

Lasse
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12

correct usage of BSD options to do this (at least on linux):

ps e $pid

or 

ps auxe  #for all processes

and yes, ps manpage is pretty confusing. (via)

raincrumb
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11

While rather sparsely documented, the contents of /proc/<pid>/environ will only contain the environment that was used to start the process.

If you need to inspect the current state of a process' environment, one way to do that is by using gdb.

# Start gdb by attaching it to a pid or core file
gdb <executable-file> <pid or core file>

# Run the following script to dump the environment
set variable $foo = (char **) environ
set $i = 0
while ($foo[$i] != 0)
print $foo[$i++]
end
Michael Renner
  • 1,760
7

Taken from the Archlinux wiki:

You can create a temporary function to parse the values in /proc/<pid>/environ. At the terminal prompt:

envof() { sed 's/\x0/\n/g' /proc/${1}/environ; }

Then with the pid of the process you want, just use:

envof <pid>
mwotton
  • 171
7
cat /proc/PID/environ

replace PID with the PID of the process you want to see. Every information about a running process is under /proc/PID/ directory

example: cat /proc/32512/environ

kargig
  • 314
6

For Solaris 5.10, this works:

pargs -e <PID>
Chris S
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Nikolai Novik
  • 161
6

Under Linux, I'd try having a look at

/proc/<pid>/environ
Joril
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4

And since my job makes me be an AIX fan boy, let us not forget:

ps eww [pid]

Or as the man page calls it, "Berkeley Standards".

For whatever reason, /proc/PID/environ does not exist in AIX.

Corey S.
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4

If you want to create formatted env like output of the environment variables for an arbitrary process (PID), you can create a convenient bash penv <pid> command (tailored to your OS) and add it to your .bashrc:

Linux add this to your ~/.bashrc:

penv () { 
    xargs --null --max-args=1 < /proc/$1/environ
}

macOS / BSD add this to your ~/.bashrc:

penv() {
   ps eww -o command $1  | tr ' ' '\n'
}

Solaris add this to your ~/.bashrc:

penv() {
   pargs -e $1
}

Usage:

$ source $HOME/.bashrc
$ pgrep VBoxSVC
10268
$ penv 10268
SSH_CONNECTION=1.1.1.242 53960 1.1.1.91 22
GREP_COLORS=sl=49;39:cx=49;39:mt=49;38;5;167;1:fn=49;39;1:ln=49;39:bn=49;39:se=50;39
LANG=en_US.UTF-8
EDITOR=vim
XDG_SESSION_ID=106
USER=root
PWD=/root
HOME=/root
SSH_CLIENT=1.1.1.242 53960 22
SSH_TTY=/dev/pts/3
MAIL=/var/mail/root
TERM=xterm-256color
SHELL=/bin/bash
SHLVL=1
LOGNAME=root
DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/0/bus
XDG_RUNTIME_DIR=/run/user/0
PATH=/root/bin:/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:.
VBOX_LOG_FLAGS=thread tsc
VBOX_LOG=-all+dev_vmm_backdoor.e.l.f+dev_vmm.e.l.f
clearlight
  • 153
0

A mac solution, probably other BSDs as well could be something like

pid=28369; ps e $pid | cut -c$(expr 1 + $(ps p $pid|tail +2|wc -c))-

The environment variables are appended to the command line, this removes the command line and we only have the environment variables left.

It is not perfect because they are space separated not LF separated

Erik Martino
  • 113
-1

/proc/PID/environ

for this, first we need to identify the PID of the process. for this you can use ps command

varun
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