Use comparison operators in AWSTOE component documents - EC2 Image Builder
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Use comparison operators in AWSTOE component documents

You can use the following comparison operators with the Assert action module and with conditional expressions that use the if Construct. A comparison operator can operate on a single value, for example stringIsEmpty, or it can compare a baseline value to a second value (variable value) to determine whether the conditional expression evaluates to true or false.

If the comparison operates on two values, the second value can be a chaining variable.

When comparing values of a different type, the following value conversions can occur prior to the comparison:

  • For numeric comparisons, if the variable value is a string, AWSTOE converts the string to a number prior to the evaluation. If the conversion is not possible, the comparison returns false. For example, if the variable value is "1.0", the conversion works, but if the variable value is "a10" the conversion fails.

  • For string comparisons, if the variable value is a number, AWSTOE converts it to a string prior to the evaluation.

Compare strings

The following comparison operators work with strings to compare values, to test for spaces or an empty string, or to compare an input value to a regex pattern. String comparisons are not case sensitive, and they don't trim spaces from the beginning or the end of the string inputs.

String comparison operators
stringIsEmpty

The stringIsEmpty operator returns true if the specified string doesn't contain any characters. For example:

# Evaluates to true
stringIsEmpty: ""

# Evaluates to false
stringIsEmpty: " "
				
# Evaluates to false
stringIsEmpty: "Hello."
stringIsWhitespace

Tests if the string specified for stringIsWhitespace contains only spaces. For example:

# Evaluates to true
stringIsWhitespace: "   "

# Evaluates to false
stringIsWhitespace: ""
				
# Evaluates to false
stringIsWhitespace: " Hello?"
stringEquals

Tests if the string specified for stringEquals is an exact match for the string specified in the value parameter. For example:

# Evaluates to true
stringEquals: 'Testing, testing...'
value: 'Testing, testing...'

# Evaluates to false
stringEquals: 'Testing, testing...'
value: 'Hello again.'

# Evaluates to false
stringEquals: 'Testing, testing...'
value: 'TESTING, TESTING....'

# Evaluates to false
stringEquals: 'Testing, testing...'
value: '   Testing, testing...'
				
# Evaluates to false
stringEquals: 'Testing, testing...'
value: 'Testing, testing...   '
stringLessThan

Tests if the string specified for stringLessThan is less than the string specified in the value parameter. For example:

# Evaluates to true
# This comparison operator isn't case sensitive
stringlessThan: 'A'
value: 'a'

# Evaluates to true - 'a' is less than 'b'
stringlessThan: 'b'
value: 'a'

# Evaluates to true
# Numeric strings compare as less than alphabetic strings
stringlessThan: 'a'
value: '0'

# Evaluates to false
stringlessThan: '0'
value: 'a'
stringLessThanEquals

Tests if the string specified for stringLessThanEquals is less than or equal to the string specified in the value parameter. For example:

# Evaluates to true - 'a' is equal to 'a'
stringLessThanEquals: 'a'
value: 'a'

# Evaluates to true - since the comparison isn't case sensitive, 'a' is equal to 'A'
stringLessThanEquals: 'A'
value: 'a'

# Evaluates to true - 'a' is less than 'b'
stringLessThanEquals: 'b'
value: 'a'

# Evaluates to true - '0' is less than 'a'
stringLessThanEquals: 'a'
value: '0'

# Evaluates to false - 'a' is greater than '0'
stringLessThanEquals: '0'
value: 'a'
stringGreaterThan

Tests if the string specified for stringGreaterThan is greater than the string specified in the value parameter. For example:

# Evaluates to false - since the comparison isn't case sensitive, 'A' is equal to 'a'
stringGreaterThan: 'a'
value: 'A'

# Evaluates to true - 'b' is greater than 'a'
stringGreaterThan: 'a'
value: 'b'

# Evaluates to true - 'a' is greater than '0'
stringGreaterThan: '0'
value: 'a'

# Evaluates to false - '0' is less than 'a'
stringGreaterThan: 'a'
value: '0'
stringGreaterThanEquals

Tests if the string specified for stringGreaterThanEquals is greater than or equal to the string specified in the value parameter. For example:

# Evaluates to true - 'a' is equal to 'A'
stringGreaterThanEquals: 'A'
value: 'a'

# Evaluates to true - 'b' is greater than 'a'
stringGreaterThanEquals: 'a'
value: 'b'

# Evaluates to true - 'a' is greater than '0'
stringGreaterThanEquals: '0'
value: 'a'

# Evaluates to false - '0' is less than 'a'
stringGreaterThanEquals: 'a'
value: '0'
patternMatches

Tests if the string specified in the value parameter matches the regex pattern specified for patternMatches. The comparison uses to the Golang regexp package, which conforms to the RE2 syntax. For more information about RE2 rules, see the google / re2 repository in GitHub.

The following example shows a pattern match that returns true:

patternMatches: '^[a-z]+$'
value: 'ThisIsValue'

Compare numbers

The following comparison operators work with numbers. The values provided for these operators must be one of the following types, according to the YAML specification. Support for numeric comparisons uses the golang big package comparison operator, for example: func (*Float) Cmp.

  • Integer

  • Float (based on float64, which supports numbers from -1.7e+308 to +1.7e+308)

  • A string that matches the following regex pattern: ^[-+]?([0-9]+[.])?[0-9]+$

Number comparison operators
numberEquals

Tests if the number specified for numberEquals is equal to the number specified in the value parameter. All of the following example comparisons return true:

# Values provided as a positive number
numberEquals: 1
value: 1

# Comparison value provided as a string
numberEquals: '1'
value: 1

# Value provided as a string
numberEquals: 1
value: '1'

# Values provided as floats
numberEquals: 5.0
value: 5.0

# Values provided as a negative number
numberEquals: -1
value: -1
numberLessThan

Tests if the number specified for numberLessThan is less than the number specified in the value parameter. For example:

# Evaluates to true
numberLessThan: 2
value: 1

# Evaluates to true
numberLessThan: 2
value: 1.9

# Evaluates to false
numberLessThan: 2
value: '2'
numberLessThanEquals

Tests if the number specified for numberLessThanEquals is less than or equal to the number specified in the value parameter. For example:

# Evaluates to true
numberLessThanEquals: 2
value: 1

# Evaluates to true
numberLessThanEquals: 2
value: 1.9

# Evaluates to true
numberLessThanEquals: 2
value: '2'

# Evaluates to false
numberLessThanEquals: 2
value: 2.1
numberGreaterThan

Tests if the number specified for numberGreaterThan is greater than the number specified in the value parameter. For example:

# Evaluates to true
numberGreaterThan: 1
value: 2

# Evaluates to true
numberGreaterThan: 1
value: 1.1

# Evaluates to false
numberGreaterThan: 1
value: '1'
numberGreaterThanEquals

Tests if the number specified for numberGreaterThanEquals is greater than or equal to the number specified in the value parameter. For example:

# Evaluates to true
numberGreaterThanEquals: 1
value: 2

# Evaluates to true
numberGreaterThanEquals: 1
value: 1.1

# Evaluates to true
numberGreaterThanEquals: 1
value: '1'

# Evaluates to false
numberGreaterThanEquals: 1
value: 0.8

Check files

The following comparison operators check the file hash or check if a file or folder exists.

File and folder operators
binaryExists

Tests whether an application is available in the current path. For example:

binaryExists: 'foo'
Note

On Linux and macOS systems, for an application named foo, this works the same as the following bash command: type foo >/dev/null 2>&1, where $? == 0 indicates a successful comparison.

On Windows systems, for an application named foo, this works the same as the PowerShell command & C:\Windows\System32\where.exe /Q foo where $LASTEXITCODE = 0 indicates a successful comparison.

fileExists

Tests whether a file exists at the specified path. You can provide an absolute or relative path. If the location you specify exists and is a file, the comparison evaluates to true. For example:

fileExists: '/path/to/file'
Note

On Linux and macOS systems, this works the same as the following bash command: -d /path/to/file, where $? == 0 indicates a successful comparison.

On Windows systems, this works the same as the PowerShell command Test-Path -Path 'C:\path\to\file' -PathType 'Leaf'.

folderExists

Tests whether a folder exists at the specified path. You can provide an absolute or relative path. If the location you specify exists and is a folder, the comparison evaluates to true. For example:

folderExists: '/path/to/folder'
Note

On Linux and macOS systems, this works the same as the following bash command: -d /path/to/folder, where $? == 0 indicates a successful comparison.

On Windows systems, this works the same as the PowerShell command Test-Path -Path 'C:\path\to\folder' -PathType 'Container'.

fileMD5Equals

Tests whether a file’s MD5 hash equals a specified value. For example:

fileMD5Equals: '<MD5Hash>'
path: '/path/to/file'
fileSHA1Equals

Tests whether a file’s SHA1 hash equals a specified value. For example:

fileSHA1Equals: '<SHA1Hash>'
path: '/path/to/file'
fileSHA256Equals

Tests whether a file’s SHA256 hash equals a specified value. For example:

fileSHA256Equals: '<SHA256Hash>'
path: '/path/to/file'
fileSHA512Equals

Tests whether a file’s SHA512 hash equals a specified value. For example:

fileSHA512Equals: '<SHA512Hash>'
path: '/path/to/file'