📜Shell Scripting
Talks about shell scripting and how it works
UESH shell contains scripting support. The shell scripts have the .uesh
extension containing a subset of UESH commands inside it. A simple UESH script containing a command that sets a UESH variable is as follows:
Script parser
When this script file is executed, the UESH script parser skims the file for any possible $variables
and initializes them with their default values using the UESHVariables.InitializeVariable
function.
The parser then attempts to skim the script lines for all the variables, and replaces them with the value. The parser also attempts to parse the script argument placeholders, defined with {num}
; which num
is the argument number, in case the ︎user executed the script with the arguments. For example, this script prints the first argument:
As soon as the parsing is done, the final line gets executed by the GetLine()
command.
Variables
UESH provides the variable facility, which holds the variable as a key and the variable value as a value. Each variable starts with the dollar sign like $var
, regardless of the platform.
When a variable gets initialized by InitializeVariable()
, the variable name gets sanitized (SanitizeVariableName()
) by appending the dollar sign in front of the variable name, which then gets initialized with the empty value.
The variable can be read from and written to by these respective functions: GetVariable()
and SetVariable()
. These can be used by your mods. Additionally, an array of values can be initialized with one variable by SetVariables()
to initialize $var[n]
variables, which:
var
: A variable namen
: How many values are there (count from 0)
When the kernel starts up, ConvertSystemEnvironmentVariables()
queries the operating system for environment variables and sets them one by one to the UESH variable store. Its list can be obtained by the GetVariables()
function.
Additionally, the variables can be uninitialized by the RemoveVariable()
function. When the target variable is removed, it has to be re-initialized before it can be used again.
Conditions
No scripting is complete with conditions, which control the execution of the command. These conditions are currently available to be used: (<value>
can either be a constant or a UESH $variable
)
eq
: The value is equal to the valueUsage:
<value> eq <value>
neq
: The value is not equal to the valueUsage:
<value> neq <value>
les
: The number is less than another numberUsage:
<value> les <value>
lesoreq
: The number is less than or equal to another numberUsage:
<value> lesoreq <value>
gre
: The number is greater than another numberUsage:
<value> gre <value>
greoreq
: The number is greater than or equal to another numberUsage:
<value> greoreq <value>
fileex
: The file existsUsage:
fileex <value>
filenex
: The file doesn't existUsage:
filenex <value>
direx
: The directory existsUsage:
direx <value>
dirnex
: The directory doesn't existUsage:
dirnex <value>
has
: The specified string contains a substringUsage:
<value> has <value>
hasno
: The specified string doesn't contain a substringUsage:
<value> hasno <value>
ispath
: The specified path is validUsage:
<value> ispath
isnotpath
: The specified path is invalidUsage:
<value> isnotpath
isfname
: The specified file name is validUsage:
<value> isfname
isnotfname
: The specified file name is invalidUsage:
<value> isnotfname
sane
: The hash matches the expected hashUsage:
<value> <value> sane
insane
: The hash doesn't match the expected hashUsage:
<value> <value> insane
fsane
: The file hash matches the expected hashUsage:
<value> <value> fsane
finsane
: The file hash doesn't match the expected hashUsage:
<value> <value> finsane
is
: The variable is of the appropriate typeUsage:
<value> is <type>
isnot
: The variable is not of the appropriate typeUsage:
<value> isnot <type>
isplat
: The host is running a selected platformUsage:
isplat <platform>
isnotplat
: The host is not running a selected platformUsage:
isnotplat <platform>
<type>
can be one of the following:
null
string
fullstring
numeric
byte
i8
ubyte
u8
int16
short
i16
int32
integer
i32
int64
long
i64
uint16
ushort
u16
uint32
uinteger
u32
uint64
ulong
u64
decimal
float
f32
double
f64
bool
regex
<platform>
can be one of the following:
win
: Windows platforms (Windows 10, 11, ...)mac
: Macintosh platforms (macOS Catalina, Big Sur, ...)unix
: Unix flavors (Linux, ...)android
: Android phones and tablets (Android 13, 14, ...)
Implementation
The conditions all have their base condition class and their interface to be implemented like below:
Basically, you must override all the variables, where:
ConditionName
: A condition name without spaces to be included in the expression
ConditionPosition
: Which word number starting from 1 should the expression be found?
ConditionRequiredArguments
: How many arguments are required? Starting from 1.
Choose one of the two method overloads to override, depending on your condition:
IsConditionSatisfied(string FirstVariable, string SecondVariable)
This function checks the two variables to see if they satisfy a condition
IsConditionSatisfied(string[] Variables)
This function checks any number of variables to see if they satisfy a condition
You can call ConditionSatisfied()
to test any built-in or custom condition. Give it any expression and test it with true
.
The if
command in the UESH shell is a major contributor to the condition system, though it can be changed in the future.
Conditional blocks and Loops
The conditional blocks and loops are one of the most essential scripting features that control the script flow based on the conditions and conditional loops. These are currently supported:
if <condition>
while <condition>
until <condition>
After the script parser detects one of these, it checks for the new block stack in the next line, like this:
The new block stack must be defined with one extra |
character directly after lines that start with one of the above conditional block statements. Otherwise, parsing will fail.
If defined correctly, the script parser walks through the commands defined in the new stack. However, if the condition is not satisfied, the whole block stack for the first conditional block that doesn't satisfy the condition will be skipped and the parser will continue executing commands that are defined in the current stack. For example, consider this:
This script first checks to see if the user has answered y
in the first line. The following will happen:
If the user answered
y
, the script parser enters the new stack defined by theif
condition in line 2.If the user answered
n
, the script parser skips the new stack defined by theif
condition and continues parsing the commands from line 8.
while
and until
blocks require the new stack to be defined. In addition to this, the script parser checks to see if the condition is no longer satisfied after the stack that these blocks defined.
If the condition is satisfied, the commands after the
while
oruntil
blocks get executed.If the condition is not satisfied, the commands after the
while
oruntil
blocks get skipped and the script parser continues parsing the commands.
Custom conditions
Custom conditions are mod-defined conditions that customize the way that you define the conditions and how you want the condition to be satisfied. Your typical condition class file looks like this:
To register your condition, you must call UESHConditional.RegisterCondition()
in your mod initialization code to add your condition with your needed code to the list of custom conditions. After that, the UESH script parser will be able to parse your custom condition.
To unregister your condition, you must call UESHConditional.UnregisterCondition()
in your mod cleanup code to remove your condition from the list of custom conditions. After that, you won't be able to use scripts that use your custom condition.
Error codes
The error code variable, UESHErrorCode
, holds information about the last process error code, whether it's a success (a zero value) or a failure (non-zero value). Currently, these values are supported:
Error codes that come from the parser
0
Indicates success
-1
Indicates that the command is not found
-2
Indicates that the command is not found and that the file is not found under any path lookup directories
-3
Indicates that the command is attempting to be run in maintenance mode and the command forbids that
-4
Indicates that the command is a strict command and the user doesn't have permissions to execute it
Error codes that come from the commands
0
Indicates success
-5
Indicates that the command is interrupted unexpectedly
-6
Indicates that the user didn't provide required arguments
Exception.GetHashCode()
Some commands throw this value from any exception. Indicates that the command failed to perform its operation.
10000 + KernelExceptionType
Some commands throw this value from any KernelException that is thrown by the command executor. Indicates that the command failed to perform its operation, but the kernel already knows about it.
Example: If
KernelExceptionType.Config
is thrown from the command executor, and the command knows how to return this exception as an error code, then it'll return the sum of10000 + 7
, which is10007
.
Command-specific error codes
1
Indicates that the command answered
n
to the confirmation (FTP and SFTP'sdel
command)
2
Indicates that either the real or the imaginary number is not valid (
imaginary
command)
3
Indicates that the unit type is not found (
unitconv
command)
4
Indicates that the hashes don't match (
verify
command)
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