These are just my notes while following along with this Youtube course on bash scripting, which is very good. The link can be found here: Bash Scripting course. I'll probably be updating it and adding comments as I move on to the more advanced lessons.
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test=$(pwd) -- this is defining the command as a variable.
echo $test -- this will return the output of the pwd command.
expr 12 \* 3 -- we use expr to do sums at the bash command line. In this example, the multiplication symbol (*) is escaped because it's a wildcard in bash.
Addition would simply look like expr 12 + 3
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#!/bin/bash
name ="Jonee"
now=$(date)
echo "Hallo, $name"
echo "Your system time and date is:"
echo "$now"
echo "Your username is: $USER"
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#!/bin/bash
mynum=200
if [ $mynum -eq 200 ]
then
echo "The condition is true."
else
echo "This is what's returned when the condition is NOT true."
fi
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#!/bin/bash
if [ -f ~/somefile ]
then
echo "File exists in Home directory."
else
echo "That file cannot be found."
fi
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#!/bin/bash
cmd=/usr/bin/htop
if [ -f cmd]
then
echo "Found. Running..."
else
echo "Not Found. Installing..."
sudo apt install cmd$
fi
$cmd
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cmd=/usr/bin/htop
if command -v $cmd
then
echo "Found. Running..."
else
echo "Not Found. Installing..."
sudo apt install cmd$
fi
$cmd
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Exit Only
echo $? -- after the command; this will provide the exit code.
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package=something
sudo apt install $package
echo "The exit code is: $?"
package=something
sudo apt install $package
if [ $? -eq 0]
then
echo "The installation of $package was successful."
else
echo "$package installation failed. Exit code is $?"
fi
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package=something >> results.log
sudo apt install $package
if [ $? -eq 0]
then
echo "The installation of $package was successful."
else
echo "$package installation failed. Exit code is $?" >> failure.log
fi
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#!/bin/bash
dir=/etc
if [ -d $dir]
then
echo "Directory exists."
else
echo "Directory does not exist."
fi
echo "The exit code for this script run is $?"
//The above script is flawed since the exit code will be 0 even in the event of a failure.
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#!/bin/bash
myvar=1
while [ $myvar -le 110 ]
do
echo $myvar
myvar=$(( $myvar +3))
sleep 0.5
done
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#!/bin/bash
while [ -f testfile ]
do
echo "As of $(date) Testfile exists."
sleep 5.6
done
echo "As of $(date) the file does NOT exist."
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#!/bin/bash
if [ -d /etc/dnf ]
then
sudo dnf update
fi
if [ -d /etc/pacman.d]
then
sudo pacman -Syu
fi
if [ -d /etc/apt ]
then
sudo apt update
sudo apt dist-upgrade
fi
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#!/bin/bash
release_file=/etc/os-release
if grep - q "Fedora" $release_file
then
sudo dnf update
fi
if grep -q "Mint" $release_file || grep -q "Ubuntu" $release_file
then
sudo apt update
sudo apt dist-upgrade
fi
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