Using command outputs in another scripts

hal_sk

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Hello,
Sometime I need to extract specific value (or more values) from my system using command outputs (in order to use this values for conditional testing in scripts).
For example: Get my CPU temperature and if it is above 60 °C then do something.
For this scenario I use command "watch -n 2 sensors" which will output something like this:
Code:
coretemp-isa-0000
Adapter: ISA adapter
Package id 0:  +34.0°C  (high = +100.0°C, crit = +100.0°C)
Core 0:        +33.0°C  (high = +100.0°C, crit = +100.0°C)
Core 1:        +34.0°C  (high = +100.0°C, crit = +100.0°C)
Core 2:        +34.0°C  (high = +100.0°C, crit = +100.0°C)
Core 3:        +34.0°C  (high = +100.0°C, crit = +100.0°C)
pch_skylake-virtual-0
Adapter: Virtual device
temp1:        +41.0°C
BAT0-acpi-0
Adapter: ACPI interface
in0:          14.40 V
asus-isa-0000
Adapter: ISA adapter
cpu_fan:     1700 RPM
temp1:        +33.0°C
nouveau-pci-0100
Let's say I want to extract temperature value in second line from bottom. Should I use some grep pattern search and other text-tweaking methods or is there cleaner way to get CPU temperature (just the integer)?

Or another scenario: I use my Linux PC as wifi access point and I want to know when specific device connects to my AP. For this I use command "sudo iw dev wlan0 station dump" which outputs something like this:
Code:
Station 2f:ba:a6:a1:cb:31 (on wlan0)
    inactive time:    3000 ms
    rx bytes:    71000
    rx packets:    1564
    tx bytes:    735079
    tx packets:    3305
    tx failed:    0
    tx bitrate:    54.0 MBit/s
    rx bitrate:    24.0 MBit/s
    authorized:    yes
    authenticated:    yes
    associated:    yes
    WMM/WME:    no
    TDLS peer:    yes
    DTIM period:    2
    beacon interval:100
    short slot time:yes
    connected time:    212 seconds
I would like to test it if MAC address (station) matches "2f:ba:a6:a1:cb:31" and "authorized: yes" is present. Should I again use some string processing functions or is there better way to get information I need in much cleaner way?
Right now I evaluating for MAC address using this command:
iw dev wlan0 station dump | grep -c '2f:ba:a6:a1:cb:31' which outputs "1" if there is match.
But I have trouble evaluating for string "authorized: yes" because string contains some strange whitespace characteres.
iw dev wlan0 station dump | grep -c 'authorized:yes' outputs "0"
iw dev wlan0 station dump | grep -c 'authorized: yes' outputs "0"
iw dev wlan0 station dump | grep -c 'authorized: yes' outputs "0"

Are there nicer solutions for issues mentioned above? I hope so, because these do not feel right to me :)
 


dcbrown73

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Grep is a nice tool, but Awk is grep on steroids.

I would learn the following tools to really help you. There are a lot more, but these can help you with text processing a majority of the time.

  • grep
  • awk
  • sed
  • cut
  • head
  • tail
  • sort
  • uniq
As noted, awk is incredibly powerful in what you are asking.
 

wizardfromoz

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Moving this to Command Line, where scripts are also handled.

Wizard
 

Fanboi

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Try running this in the background (apply to others)

Code:
#! /bin/bash

while [ 1 ]
do

# Gives you the integer (%d) value of your Temps)
iiTemps=$(sensors | grep core | cut -d+ -f2 | cut -d. -f1)

if [ $iiTemps -gt 60 ]
then
# What commands to execute
fi

# Decrease to whatever N seconds precision you need.
sleep 5

done

Sorry for lack of indentation/typos, on my phone.
 
OP
hal_sk

hal_sk

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Most of above mentioned command were not know to me. Thanks. I will put them into use.
And is there more reliable method to get system data in general? It would be nice if outputed data from commands:
sensors
or
iw dev wlan0 station dump
or similar... could be retrieved in JSON format, let's say using flag "-json" in command.
 

Fanboi

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IDK about json objects. That's up to software and most lower/lowish-level stuff only outputs to stdout. But you can redirect it to a text file if you feel you can't parse everything at once:

Code:
# Dump sensors output to file

# Create or overwrite file
sensors > /tmp/dump.txt

# Create or append to file
sensors >> /tmp/dump.txt

You can't jq it, but you could parse it with your own script using grep, awk, etc. or get fancy and bring Python into the mix.
 
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