Linux - Process

OS - Process (Main Thread) / Program in linux

With the ps utility

# for all process
ps -eo args
# for one process
ps -p [PID] -o args

ps axco pid,command

How to get the PID (process identification number) of a process (

• Linux - ps (process statut)

# ps aux'' includes the full command line (path and parameters), 
ps aux | grep pattern

• pgrep

# pgrep by default only looks at the first 15 characters of the executable's names
# That's why you need the -f option
pgrep -f pattern

Function example

get_pid ()
{
    if [ "$ANA_VARIANT" = "AIX" ]; then
    	echo `${bin_ps} -u${ana_username} | ${bin_grep} $1 | ${bin_awk} '{print $2}'`
    else
    	echo `${bin_ps} -u${ana_username} | ${bin_grep} $1 | ${bin_awk} '{print $1}'`
    fi
}

Bash - Kill a process

Priority gives the process more or less CPU time than other processes.

See: Nice_(Unix)

All utilities obtains processes information via the Filesystem (procfs)

From the bash man page: $ Expands to the process ID of the shell. In a () subshell, it expands to the process ID of the current shell, not the sub-shell.

echo $$

The $$ variable often finds use in scripts to construct “unique” temp file names

BASHPID: Process ID of the current instance of Bash. <warning>bash 4</note>

echo $BASHPID

The $PPID of a process is the process ID (pid) of its parent process.

The PID (process ID) of last job run in background

cat /proc/{pid}/environ | tr \\0 \\n
# tr \\0 \\n because you want get rid of the null characters (\0)

Example for a process named nqsserver:

cat /proc/$(pidof nqsserver)/environ | tr \\0 \\n

How to copy an environment variable of a process to the shell dynamically

export LD_LIBRARY_PATH=$(cat /proc/$(pidof nqsserver)/environ | tr \\0 \\n | grep LD_LIBRARY_PATH= | cut -c17-)

• Linux - ps (process statut)
• pgrep

pidof: Pidof finds the process id’s (pids) of the named programs.

pidof nqsserver

23686

• Java

pidof java

26986 26856 26284 24546 6358

sudo netstat -nlp | grep :9703

tcp        0      0 0.0.0.0:9703                0.0.0.0:*                   LISTEN      23066/nqsserver

The PID is 23066

ps -f --pid $PID
ps -f -p $PID
ps -p $PID -o pid,vsz=MEMORY -o user,group=GROUP -o comm,args=ARGS

Example:

ps -f --pid 23066
ps -f -p 23066

UID        PID  PPID  C STIME TTY          TIME CMD
oracle   23066 22951  0 Feb15 ?        00:07:33 nqsserver -quiet

File System - Open File

• by port

lsof -i port

• by process id

lsof -p $(pgrep nqsserver) | awk '{print $9}' 
# for 3 process
lsof -p 456,123,789 

• by user

lsof -u 1234,userName

What are the Metrics / Counters of Linux ?

With the while bash statement (Replace with your pid)

pid=4277
count=0
while kill -0 $pid 2> /dev/null; do
    count=$(( $count + 1 ))
    echo "${count} - Process is running"
    sleep 10
done
echo "${count} - Process has exited"

Two methods:

• the file.PID method. Check if the file exist in the directory /home/lsc/

pwdx $PID

• by port

lsof -i port