${If}

Conditionally executes a block of statements, depending on the value of an expression.

Syntax

${If} expression

The following "expressions" are available:

Standard (built-in) string tests (which are case-insensitive):
     a == b; a != b
Additional case-insensitive string tests (using System.dll):
     a S< b; a S>= b; a S> b; a S<= b
Case-sensitive string tests:
     a S== b; a S!= b
Standard (built-in) signed integer tests:
     a = b; a <> b; a < b; a >= b; a > b; a <= b
Standard (built-in) unsigned integer tests:
     a U< b; a U>= b; a U> b; a U<= b
64-bit integer tests (using System.dll):
    a L= b; a L<> b; a L< b; a L>= b; a L> b; a L<= b
Built-in NSIS flag tests:
    ${Abort}; ${Errors}; ${RebootFlag}; ${Silent}
Built-in NSIS other tests:
    ${FileExists} a
Any conditional NSIS instruction test:
    ${Cmd} a
Section flag tests:
    ${SectionIsSelected} a; ${SectionIsSectionGroup} a;
    ${SectionIsSectionGroupEnd} a; ${SectionIsBold} a;
    ${SectionIsReadOnly} a; ${SectionIsExpanded} a;
    ${SectionIsPartiallySelected} a

Examples

Check if condition is met

StrCpy $0 true

${If} $0 == true
    MessageBox MB_OK "It's true"
${Else}
    MessageBox MB_OK "This will never be true"
${EndIf}

Integer tests

${If} 1 > 0
    MessageBox MB_OK "1 is greater than 0"
${EndIf}

${If} 2 > 1
${AndIf} 2 < 3
    MessageBox MB_OK "2 is greater than 1 and smaller than 3"
${EndIf}

File conditions

${If} ${FileExists} $SYSDIR\notepad.exe
    Exec $SYSDIR\notepad.exe
${Else}
    MessageBox MB_OK "Could not find notepad.exe"
${EndIf}

${If} ${FileExists} $PROGAMFILES\*.*
    MessageBox MB_OK "Directory $$PROGRAMFILES exists"
${EndIf}

Section test

Section "My Section" mySection
    MessageBox MB_OK "Executing section"

    ${If} ${SectionIsSelected} ${mySection}
        MessageBox MB_OK "It's selected, dummy!"
    ${EndIf}
SectionEnd

Credits

Written by dselkirk and eccles