CheatGroovy Scripting for the JVM
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Start here
groovy <file>.groovy
Run a script
groovy -e '<code>'
Run one-liner
groovyshInteractive shell
groovy -vShow versions
groovy -n -e '<code>'
Run per input line
groovy -cp <path> <file>
Add classpath
groovy -Dkey=value <file>
Set property
@Grab('g:m:v')
Fetch a library
Concepts
- Script .groovy source
- Bytecode in memory
- JVM needs a JDK
- Libraries Maven repos
Running
groovy <file>.groovy [args]
Run a script
Arguments arrive in the args array.
groovy -e '<code>'
Run an inline script
groovy -vShow Groovy and JVM versions
groovy -cp <path> <file>
Set the classpath
Must be the first argument.
groovy -Dkey=value <file>
Define a system property
groovy -d <file>
Print full stack traces
groovy -l <port>
Process each line sent to a port
Default port is 1960.
groovy -b <class> <file>
Use a custom base script class
groovy -pa <file>
Keep method parameter names
groovy --helpList all options
One-liners
groovy -n -e '<code>' <file>
Run code per line, as line
groovy -p -e '<code>' <file>
Run per line and print result
Reassign line to change what is printed.
groovy -a -n -e '<code>' <file>
Split each line into split
Default separator is whitespace; -a takes a pattern.
groovy -i .bak -p -e '<code>'
<file>
Edit files in place with backup
Without an extension no backup is kept.
groovy -c <charset> <file>
Set source encoding
Shell
groovyshStart the interactive shell
groovysh -qStart without the banner
groovysh -e '<code>'
Evaluate code at start
/helpList shell commands
/showList shared variables
/load <file>
Load a file into the buffer
/save <file>
Save the buffer to a file
/historyShow and recall history
/inspect <expr>
Browse an object
/grab <g:m:v>
Add a dependency to the shell
/exitLeave the shell
Dependencies
@Grab('<g>:<m>:<v>')
Pull in a library
Resolved from Maven Central and cached under ~/.groovy.
@GrabResolver(name='<n>',
root='<url>')
Add a repository
@GrabExclude('<group>:<module>')
Skip a transitive dependency
@GrabConfig(systemClassLoader=true)
Use the system class loader
Needed for JDBC drivers.
grape install <group> <module>
[<version>]
Download into the cache
grape listList cached modules
grape resolve <group> <module>
<version>
Print jar locations
grape uninstall <group> <module>
<version>
Remove from the cache
Syntax
def x = 1Declare a variable
def is the same as Object.
println "Hi ${name}"
Interpolate in a GString
Only double-quoted strings interpolate.
'''line1 line2'''
Multi-line string
Triple double quotes interpolate too.
/a\d+/Slashy string for regex
def f = { a, b -> a + b }
Closure
list.collect { it * 2 }
Map over a collection
it is the implicit single parameter.
a?.bSafe navigation
a ?: bElvis: default if falsy
list*.nameSpread: property of each item
a <=> bCompare: -1, 0 or 1
a == bValue equality
Use is for identity.
x ?= 5Assign if x is falsy
obj.&methodMethod pointer
class Foo { String name }
Class with auto getters
@CompileStaticStatic type checking
@TypeCheckedCheck types, stay dynamic
Collections
[1, 2, 3]List literal
[a: 1, b: 2]Map literal
[] as SetConvert to another type
(1..5)Inclusive range
Use 1..<5 to exclude the end.
list.each { println it }
Loop over items
list.findAll { it > 1 }
Filter
list.find { it > 1 }
First match
list.inject(0) { s, x -> s + x }
Fold to one value
list.sum()Add up elements
list.groupBy { it.size() }
Group into a map
list.sort { it.name }
Sort by key
list.collectEntries { [(it): it.size()] }
Build a map
map.each { k, v -> println "$k=$v" }
Loop over a map
list.any { it > 1 }
Any element matches
list.unique()Drop duplicates
Files & text
new File('<path>').text
Read a whole file
new File('<path>').eachLine { }
Read line by line
new File('<path>').text =
'<data>'
Write a file
new File('<path>') <<
'<data>'
Append to a file
new File('.').eachFileRecurse { }
Walk a directory tree
'echo hi'.execute().text
Run a shell command
str =~ /<regex>/
Find a match
str ==~ /<regex>/
Match the whole string
new groovy.json.JsonSlurper().parseText(s)
Parse JSON
groovy.json.JsonOutput.toJson(obj)
Write JSON
Recipes
@Grab('org.apache.commons:commons-lang3:3.14.0')import org.apache.commons.lang3.StringUtilsprintln StringUtils.capitalize('groovy')groovy -n -e 'if (line =~ /ERROR/) println line' app.loggroovy -i .bak -p -e 'line.replace("foo", "bar")' *.txtdef url = 'https://api.example.com/items'def data = new groovy.json.JsonSlurper().parse(url.toURL())data.each { println it.name }
