A NSIS Script File (.nsi) is just a text file with script code.
Commands
Commands lines are in the format 'command [parameters]'
File "myfile"
Comments
Lines beginning with ; or # are comments. You can put comments after commands. You can also use C-style comments to comment one or more lines.
; Comment # Comment /* Comment Comment */ File "myfile" ; Comment
If want a parameter to start with ; or # put it in quotes.
Plug-ins
To call a plugin, use 'plugin::command [parameters]'. For more info see Plugin DLLs.
nsExec::Exec "myfile"
Numbers
For parameters that are treated as numbers, use decimal (the number) or hexadecimal (with 0x prepended to it, i.e. 0x12345AB), or octal (numbers beginning with a 0 and no x).
Colors should be set in hexadecimal RGB format, like HTML but without the #.
IntCmp 1 0x1 lbl_equal SetCtlColors $HWND CCCCCC
Strings
To represent strings that have spaces, use quotes:
MessageBox MB_OK "Hi there!"
Quotes only have the property of containing a parameter if they begin the parameter. They can be either single quotes, double quotes, or the backward single quote.
You can escape quotes using $\:
MessageBox MB_OK "I'll be happy" ; this one puts a ' inside a string MessageBox MB_OK 'And he said to me "Hi there!"' ; this one puts a " inside a string MessageBox MB_OK `And he said to me "I'll be fucked!"` ; this one puts both ' and "s inside a string MessageBox MB_OK "$\"A quote from a wise man$\" said the wise man" ; this one shows escaping of quotes
It is also possible to put newlines, tabs etc. in a string using $\r, $\n, $\t etc. More information...
Variables
Variables start with $. User variables should be declared and are case-sensitive.
Var MYVAR StrCpy $MYVAR "myvalue"
Long commands
To extend a command over multiple lines, use a backslash (\) at the end of the line, and the next line will effectively be concatenated the end of it. For example:
CreateShortCut "$SMPROGRAMS\NSIS\ZIP2EXE project workspace.lnk" \
"$INSTDIR\source\zip2exe\zip2exe.dsw"
MessageBox MB_YESNO|MB_ICONQUESTION \
"Do you want to remove all files in the folder? \
(If you have anything you created that you want \
to keep, click No)" \
IDNO NoRemoveLabel
Configuration file
If a file named "nsisconf.nsh" in the same directory as makensis.exe exists, it will be included by default before any scripts (unless the /NOCONFIG command line parameter is used).