QGIS/resources/function_help/json/substr

{
  "name": "substr",
  "type": "function",
  "groups": ["String"],
  "description": "Returns a part of a string.",
  "arguments": [ {"arg":"string","description":"the full input string"},
  {"arg":"start","description":"integer representing start position to extract beginning with 1; if start is negative, the return string will begin at the end of the string minus the start value"},
  {"arg":"length","optional":true,"description":"integer representing length of string to extract; if length is negative, the return string will omit the given length of characters from the end of the string"}
  ],
  "examples": [ { "expression":"substr('HELLO WORLD',3,5)", "returns":"'LLO W'"},
                { "expression":"substr('HELLO WORLD',6)", "returns":"' WORLD'"},
                { "expression":"substr('HELLO WORLD',-5)","returns":"'WORLD'"},
                { "expression":"substr('HELLO',3,-1)", "returns":"'LL'"},
                { "expression":"substr('HELLO WORLD',-5,2)","returns":"'WO'"},
                { "expression":"substr('HELLO WORLD',-5,-1)","returns":"'WORL'"}
  ]
}