utshell User Guide ​

Introduction ​

utshell is a shell compatible with Bash, capable of executing basic built-in commands and starting external commands. It also implements functions such as task, pipe, and signal processing.

Installation and Uninstallation ​

Installing utshell ​

Run the rpm command to install utshell. Assume that openEuler 23.09 is used.

Enter y as prompted to install.

Uninstalling utshell ​

Run rpm -e utshell to uninstall utshell.

rpm -e utshell

Usage ​

Using Common Commands ​

In the utshell environment, enter a command to execute.

utshell has the following built-in commands:

Defining and Using Variables ​

Defining a Variable ​

Use = to define a variable. No space is allowed in the expression.

var=4

Using a Variable ​

echo ${var}

Defining and Using Arrays ​

Defining an Array ​

distros=(ubuntu fedora suse "arch linux")

Using an Array ​

echo ${distros[2]}

Defining and Using Functions ​

Defining a Function ​

func() { echo $1; }

Using a Function ​

func 1

Passing Parameters to a Function ​

When calling a function, use a space to separate the function and the parameters.

func firstParam secondParam

In the function body, use ${number} to represent the parameters, for example, $1 for the first parameter and $2 for the second parameter. For the tenth and subsequent parameters, the number must be enclosed in braces.

func() {
echo $1 ${10} # Ten parameters are required.
}
# Call the function.
func 1 2 3 4 5 6 7 8 9 0

Using Logical Conditions ​

if ​

The syntax is as follows:

if condition; then
do-if-true;
elif second-condition; then
do-else-if-true
elif third-condition; then
do-else-if-third-true
else
do-else-false
fi

condition can be a command, for example:

if [ "$s" = "string" ]; then
echo "string is equivalent to $s"
else
echo "string is not equivalent to $s"
fi

condition can also be a conditional operator.

Some conditional operators are as follows.

-f: Checks whether a file exists and is a regular file.
-d: Checks whether the provided argument is a directory.
-h: Checks whether the provided argument is a symbolic link.
-s: Checks whether a file exists and is not empty.
-r: Checks whether a file is readable.
-w: Checks whether a file is writable.
-x: Checks whether a file is executable.

The following conditional operators can be used for comparing numbers.

-lt: less than
-gt: greater than
-ge: greater than or equal to
-le: less than or equal to
-ne: not equal to

The following conditional operators can be used for comparing strings.

==: Whether two strings are identical.
=: Whether two strings are identical (same as ==).
!=: Whether two strings are different.
-z: Returns true if the string is empty.
-n: Returns true if the string length is not 0.

Using Loops ​

for ​

for number in 1 2 3 4 5
do
echo $number
done
# When used with a list:
for number in {1..500..2}
do
echo $number
done

{1..500..2} indicates that the start number is 1, the end number is 500 (included), and the step is 2.

until ​

until [condition]; do
commands
done

When the condition is true, the loop is executed.

while ​

while [ condition ]; do
commands
done

When the condition is true, the loop is executed.