Split string in Lua

Question

I need to do a simple split of a string  but there doesn t seem to be a function for this  and the manual way I tested didn t seem to work  How would I do it

User · Answer

You could use penlight library  This has a function for splitting string using delimiter which outputs list   It has implemented many of the function that we may need while programming and missing in Lua   Here is the sample for using it    gt    gt  stringx   require  pl stringx   gt    gt  str    welcome to the world of lua   gt    gt  arr   stringx split str        gt    gt  arr  welcome to the world of lua   gt

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If you program in Lua  you are out of luck here  Lua is THE one programming language that just happens to be notoriously infamous because its authors never implemented  quot the quot  split function in the standard library  and instead wrote 16 screenfulls of explanations and lame excuses as to why they didn t and wouldn t  interspersed with numerous half-working examples that are virtually guaranteed to work for almost everyone but break in your corner case  This is just Lua state of the art  and everyone who programs in Lua simply ends up clenching their teeth and iterating over characters  There are lots of solutions in existence that are sometimes better  but exactly zero solutions that are reliably better

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I used the above examples to craft my own function  But the missing piece for me was automatically escaping magic characters   Here is my contribution   function split text  delim      -- returns an array of fields based on text and delimiter  one character only      local result          local magic         -             if delim    nil then         delim     s      elseif string find delim  magic  1  true  then         -- escape magic         delim        delim     end      local pattern         delim           for w in string gmatch text  pattern  do         table insert result  w      end     return result end

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Simply sitting on a delimiter  local str    one two  local regxEverythingExceptComma             for x in string gmatch str  regxEverythingExceptComma  do     print x  end

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a way not seen in others  function str split str  sep      if sep    nil then         sep     s      end       local res          local func   function w          table insert res  w      end       string gsub str        sep        func      return res  end

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I like this short solution  function split s  delimiter      result           for match in  s  delimiter  gmatch    -    delimiter  do         table insert result  match       end     return result  end

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A lot of these answers only accept single-character separators  or don t deal with edge cases well  e g  empty separators   so I thought I would provide a more definitive solution   Here are two functions  gsplit and split  adapted from the code in the Scribunto MediaWiki extension  which is used on wikis like Wikipedia  The code is licenced under the GPL v2  I have changed the variable names and added comments to make the code a bit easier to understand  and I have also changed the code to use regular Lua string patterns instead of Scribunto s patterns for Unicode strings  The original code has test cases here   -- gsplit  iterate over substrings in a string separated by a pattern --  -- Parameters  -- text  string     - the string to iterate over -- pattern  string  - the separator pattern -- plain  boolean   - if true  or truthy   pattern is interpreted as a plain --                    string  not a Lua pattern --  -- Returns  iterator -- -- Usage  -- for substr in gsplit text  pattern  plain  do --   doSomething substr  -- end local function gsplit text  pattern  plain    local splitStart  length   1   text   return function        if splitStart then       local sepStart  sepEnd   string find text  pattern  splitStart  plain        local ret       if not sepStart then         ret   string sub text  splitStart          splitStart   nil       elseif sepEnd  lt  sepStart then         -- Empty separator          ret   string sub text  splitStart  sepStart          if sepStart  lt  length then           splitStart   sepStart   1         else           splitStart   nil         end       else         ret   sepStart  gt  splitStart and string sub text  splitStart  sepStart - 1  or            splitStart   sepEnd   1       end       return ret     end   end end  -- split  split a string into substrings separated by a pattern  --  -- Parameters  -- text  string     - the string to iterate over -- pattern  string  - the separator pattern -- plain  boolean   - if true  or truthy   pattern is interpreted as a plain --                    string  not a Lua pattern --  -- Returns  table  a sequence table containing the substrings  local function split text  pattern  plain    local ret        for match in gsplit text  pattern  plain  do     table insert ret  match    end   return ret end   Some examples of the split function in use   local function printSequence t    print unpack t   end  printSequence split  foo  bar baz      s           -- foo     bar     baz printSequence split  foo  bar baz      s    true   -- foo  bar baz printSequence split  foo                           -- f       o       o

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Because there are more than one way to skin a cat  here s my approach   Code      usr bin env lua  local content       Lorem ipsum dolor sit amet  consectetur adipisicing elit  sed do eiusmod tempor incididunt ut labore et dolore magna  aliqua  Ut enim ad minim veniam  quis nostrud exercitation  ullamco laboris nisi ut aliquip ex ea commodo consequat       local function split str  sep     local result         local regex         s      format sep     for each in str gmatch regex  do       table insert result  each     end    return result end  local lines   split content    n   for   line in ipairs lines  do    print line  end   Output   Lorem ipsum dolor sit amet  consectetur adipisicing elit   sed do eiusmod tempor incididunt ut labore et dolore magna aliqua  Ut enim ad minim veniam  quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat    Explanation    The gmatch function works as an iterator  it fetches all the strings that match regex  The regex takes all characters until it finds a separator

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Here is the function   function split pString  pPattern     local Table       -- NOTE  use  n   0  in Lua-5 0    local fpat      -      pPattern    local last end   1    local s  e  cap   pString find fpat  1     while s do       if s    1 or cap       then      table insert Table cap        end       last end   e 1       s  e  cap   pString find fpat  last end     end    if last end  lt    pString then       cap   pString sub last end        table insert Table  cap     end    return Table end   Call it like   list split string to split pattern to match    e g    list split  1 2 3 4           For more go here  http   lua-users org wiki SplitJoin

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Here is my really simple solution  Use the gmatch function to capture strings which contain at least one character of anything other than the desired separator  The separator is   any  whitespace   s in Lua  by default   function mysplit  inputstr  sep          if sep    nil then                 sep     s          end         local t            for str in string gmatch inputstr         sep         do                 table insert t  str          end         return t end

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You can use this method   function string split delimiter    local result         local from    1   local delim from  delim to   string find  self  delimiter  from      while delim from do     table insert  result  string sub  self  from   delim from-1         from    delim to   1     delim from  delim to   string find  self  delimiter  from      end   table insert  result  string sub  self  from        return result end  delimiter   string split stringtodelimite pattern

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Super late to this question  but in case anyone wants a version that handles the amount of splits you want to get       -- Split a string into a table using a delimiter and a limit string split   function str  pat  limit    local t        local fpat      -      pat   local last end   1   local s  e  cap   str find fpat  1    while s do     if s    1 or cap       then       table insert t  cap      end      last end   e 1     s  e  cap   str find fpat  last end       if limit    nil and limit  lt    t then       break     end   end    if last end  lt    str then     cap   str sub last end      table insert t  cap    end    return t end

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Depending on the use case  this could be useful   It cuts all text either side of the flags   b    This is a string used for testing   --Removes unwanted text c    b match  a       used     print  c    Output   string

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If you just want to iterate over the tokens  this is pretty neat  line    quot one  two and 3  quot   for token in string gmatch line   quot    s   quot   do    print token  end  Output   one  two and 3   Short explanation  the  quot    s   quot  pattern matches to every non-empty string in between space characters

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If you are splitting a string in Lua  you should try the string gmatch   or string sub   methods   Use the string sub   method if you know the index you wish to split the string at  or use the string gmatch   if you will parse the string to find the location to split the string at   Example using string gmatch   from Lua 5 1 Reference Manual    t       s    from world  to Lua   for k  v in string gmatch s     w     w     do    t k    v  end

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Just as string gmatch will find patterns in a string  this function will find the things between patterns   function string split pat    pat   pat or   s     local st  g   1  self gmatch        pat         local function getter segs  seps  sep  cap1           st   sep and seps    sep     return self sub segs   seps or 0  - 1   cap1 or sep        end   return function   if st then return getter st  g    end end end   By default it returns whatever is separated by whitespace

[string] Split string in Lua?

Examples related to string

Examples related to lua