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docs/Linux-Commands/Process-Management/033-the-ps-command.md

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+# The `ps` command
+
+The `ps` command is used to identify programs and processes that are running on the system and the resources they are using. 
+Its frequently [pipelined](<https://en.wikipedia.org/wiki/Pipeline_(Unix)>) with other commands like `grep` to search for a program/process or `less` 
+so that the user can analyze the output one page at a time.
+
+Let's say you have a program like openshot which is notorious for hogging system resources when exporting a video, and you want to close it, but the GUI has become unresponsive.
+
+### Example
+
+1. You want to find the PID of openshot and kill it.
+
+```
+ps aux | grep openshot
+kill - <openshot PID>
+```
+
+2. To Show all the running processes:
+
+```
+ps -A
+```
+
+
+### Syntax
+
+`ps [options]`
+
+When run without any options, it's useless and will print: `CMD` - the executable processes/(program) running, their `PID` - process ID, `TTY` - terminal type and `Time` - How long the process has utilized the CPU or thread.
+
+### Common Option
+
+If you are going to remember only one thing from this page let it be these three letter `aux`:
+`a` - which displays all processes running, including those being run by other users.
+`u` - which shows the effective user of a process, i.e. the person whose file access permissions are used by the process.
+`x` - which shows processes that do not have a `TTY` associated with them.
+
+### Additional Options:
+
+|**Option**   |**Description**   |
+|:---|:---|
+|`a`|Shows list all processes with a terminal (tty)|
+|`-A`|Lists all processes. Identical to `-e`|
+|`-a`|Shows all processes except both session leaders and processes not associated with a terminal|
+|`-d`|Select all processes except session leaders|
+|`--deselect`|Shows all processes except those that fulfill the specified conditions. Identical to `-N`|
+|`-e`|Lists all processes. Identical to `-A`|
+|`-N`|Shows all processes except those that fulfill the specified conditions. Identical to `-deselect`|
+|`T`|Select all processes associated with this terminal. Identical to the `-t` option without any argument|
+|`r`|Restrict the selection to only running processes|
+|`--help simple`|Shows all the basic options|
+|`--help all`|Shows every available options|
+
+Another useful command which give a realtime snapshot of the processes and the resources they are using about every ten seconds is `top`.

docs/Linux-Commands/Process-Management/034-the-kill-command.md

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+#  The `kill` command
+
+`kill` command in Linux (located in /bin/kill), is a built-in command which is used to terminate processes manually. The `kill` command sends a signal to a process which terminates the process. If the user doesn’t specify any signal which is to be sent along with kill command then default _TERM_ signal is sent that terminates the process.
+
+Signals can be specified in three ways:
+-   **By number (e.g. -5)**
+-   **With SIG prefix (e.g. -SIGkill)**
+-   **Without SIG prefix (e.g. -kill)**
+  
+### Syntax
+
+```
+kill [OPTIONS] [PID]...
+```
+
+###  Examples:
+1. To display all the available signals you can use below command option:
+
+```
+kill -l
+```
+
+2. To show how to use a _PID_ with the _kill_ command.
+
+```
+$kill pid
+```
+
+3. To show how to send signal to processes.
+```
+kill {-signal | -s signal} pid
+```
+
+4. Specify Signal:
+	
+- using numbers as signals 
+```
+kill -9 pid
+```
+- using SIG prefix in signals
+```
+kill -SIGHUP pid
+```
+- without SIG prefix in signals
+```
+kill -HUP pid
+```
+
+
+###  Arguments:
+The list of processes to be signaled can be a mixture of names and PIDs.
+
+       pid    Each pid can be expressed in one of the following ways:
+
+              n      where n is larger than 0.  The process with PID n is signaled.
+
+              0      All processes in the current process group are signaled.
+
+              -1     All processes with a PID larger than 1 are signaled.
+
+              -n     where n is larger than 1.  All processes in process group  n  are  signaled.
+                     When  an  argument  of  the  form '-n' is given, and it is meant to denote a
+                     process group, either a signal must be specified first, or the argument must
+                     be  preceded  by  a '--' option, otherwise it will be taken as the signal to
+                     send.
+
+       name   All processes invoked using this name will be signaled.
+###  Options:
+	   -s, --signal signal
+              The signal to send.  It may be given as a name or a number.
+
+       -l, --list [number]
+              Print a list of signal names, or convert the given signal number to  a  name.   The
+              signals can be found in /usr/include/linux/signal.h.
+
+       -L, --table
+              Similar to -l, but it will print signal names and their corresponding numbers.
+
+       -a, --all
+              Do  not  restrict the command-name-to-PID conversion to processes with the same UID
+              as the present process.
+
+       -p, --pid
+              Only print the process ID (PID) of the named processes, do not send any signals.
+
+       --verbose
+              Print PID(s) that will be signaled with kill along with the signal.
+
+

docs/Linux-Commands/Process-Management/035-the-killall-command.md

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+# The `killall` command
+
+`killall` sends a signal to **all** processes running any of the specified commands.  If no signal name is specified, `SIGTERM` is sent. In general, `killall` command kills all processes by knowing the name of the process.
+
+Signals can be specified either by name (e.g. `-HUP` or `-SIGHUP`) or by number (e.g. `-1`) or by option `-s`.
+
+If the command name is not a regular expression (option `-r`) and contains a slash (`/`), processes executing that particular file will be selected for killing, independent of their name.
+
+`killall` returns a zero return code if at least one process has been killed for each listed command, or no commands were listed and at least one process matched the `-u` and `-Z` search criteria. `killall` returns non-zero otherwise.
+
+A `killall` process never kills itself (but may kill other `killall` processes).
+
+### Examples:
+
+1. Kill all processes matching the name `conky` with `SIGTERM`:
+
+```sh
+killall conky
+# OR
+killall -SIGTERM conky
+# OR
+kilall -15 conky
+```
+
+I was able to kill Wine ( which are Windows exe files running on Linux ) applications this way too.
+
+```sh
+killall TQ.exe
+```
+
+2. List all the supported signals:
+
+```sh
+$ killall -l
+HUP INT QUIT ILL TRAP ABRT BUS FPE KILL USR1 SEGV USR2 PIPE ALRM TERM STKFLT
+CHLD CONT STOP TSTP TTIN TTOU URG XCPU XFSZ VTALRM PROF WINCH POLL PWR SYS
+```
+
+As for the numbers.
+
+```sh
+$ for s in $(killall -l); do echo -n "$s " && kill -l $s; done
+HUP 1
+INT 2
+QUIT 3
+ILL 4
+TRAP 5
+ABRT 6
+BUS 7
+FPE 8
+KILL 9
+USR1 10
+SEGV 11
+USR2 12
+PIPE 13
+ALRM 14
+TERM 15
+STKFLT 16
+CHLD 17
+CONT 18
+STOP 19
+TSTP 20
+TTIN 21
+TTOU 22
+URG 23
+XCPU 24
+XFSZ 25
+VTALRM 26
+PROF 27
+WINCH 28
+POLL 29
+PWR 30
+SYS 31
+```
+
+3. Ask before killing, to prevent unwanted kills:
+
+```sh
+$ killall -i conky
+Kill conky(1685) ? (y/N)
+```
+
+4. Kill all processes and wait until the processes die.
+
+```sh
+killall -w conky
+```
+
+5. Kill based on time:
+
+```sh
+# Kill all firefox younger than 2 minutes
+killall -y 2m  firefox
+
+# Kill all firefox older than 2 hours
+killall -o 2h  firefox
+```
+
+### Syntax:
+
+```sh
+killall [OPTION]... [--] NAME...
+killall -l, --list
+killall -V, --version
+```
+
+### Additional Flags and their Functionalities:
+
+|**Short Flag**   |**Long Flag**   |**Description**   |
+|:---|:---|:---|
+|`-e`|`--exact`|require  an  exact  match for very long names|
+|`-I`|`--ignore-case`|case insensitive process name match|
+|`-g`|`--process-group`|kill process group instead of process|
+|`-y`|`--younger-than`|kill processes younger than TIME|
+|`-o`|`--older-than`|kill processes older than TIME|
+|`-i`|`--interactive`|ask for confirmation before killing|
+|`-l`|`--list`|list all known signal names|
+|`-q`|`--quiet`|don't print complaints|
+|`-r`|`--regexp`|interpret NAME as an extended regular expression|
+|`-s`|`--signal SIGNAL`|send this signal instead of SIGTERM|
+|`-u`|`--user USER`|kill only process(es) running as USER|
+|`-v`|`--verbose`|report if the signal was successfully sent|
+|`-w`|`--wait`|wait for processes to die|
+|`-n`|`--ns PID`|match processes that belong to the same namespaces as PID
+|`-Z`|`--context`|REGEXP kill only process(es) having context (must precede other arguments)
+
+### Related commands
+
+[kill](/ebook/en/content/034-the-kill-command.md), `pidof`

docs/Linux-Commands/Process-Management/093-the-nohup-command.md

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+# The `nohup` command
+
+When a shell exits (maybe while logging out of an SSH session), the HUP ('hang up') signal is send to all of its child processes, causing them to terminate. If you require a long-running process to continue after exiting shell, you'll need the `nohup` command. Prefixing any command with `nohup` causes the command to become _immune_ to HUP signals. Additionally, STDIN is being ignored and all output gets redirected to local file `./nohup.out`.
+
+### Examples:
+
+1. Applying nohup to a long-running debian upgrade:
+
+```
+nohup apt-get -y upgrade
+```
+
+### Syntax:
+
+```
+nohup COMMAND [ARG]...
+nohup OPTION
+```