How to dump a table to console

Question

I m having trouble displaying the contents of a table which contains nested tables  n-deep   I d like to just dump it to std out or the console via a print statement or something quick and dirty but I can t figure out how  I m looking for the rough equivalent that I d get when printing an NSDictionary using gdb

User · Answer

The simplest way  with circular reference handling and all  function dump t  indent  done      done   done or        indent   indent or 0      done t    true      for key  value in pairs t  do         print string rep  quot  t quot   indent            if  type value      quot table quot  and not done value   then             done value    true             print key   quot   n quot                dump value  indent   2  done              done value    nil         else             print key   quot  t  t quot   value   quot  n quot           end     end end

User · Answer

Feel free to browse the Lua Wiki on table serialization  It lists several ways on how to dump a table to the console   You just have to choose which one suits you best  There are many ways to do it  but I usually end up using the one from Penlight    gt  t     a     b     c    Hello world    1    2  d     3        gt  require  pl pretty  dump t      a         d           3            b           c    Hello world          1            2

User · Answer

--  print a table function printTable list  i       local listString      --  begin of the list so write the       if not i then         listString   listString            end      i   i or 1     local element   list i   --  it may be the end of the list     if not element then         return listString            end --  if the element is a list too call it recursively     if type element      table   then         listString   listString    printTable element      else         listString   listString    element     end      return listString            printTable list  i   1   end   local table    1  2  3  4  5    a    b      G    F    print printTable table     Hi man  I wrote a siple code that do this in pure Lua  it has a bug  write a coma after the last element of the list  but how i wrote it quickly as a prototype I will let it to you adapt it to your needs

User · Answer

Most pure lua print table functions I ve seen have a problem with deep recursion and tend to cause a stack overflow when going too deep  This print table function that I ve written does not have this problem  It should also be capable of handling really large tables due to the way it handles concatenation  In my personal usage of this function  it outputted 63k lines to file in about a second   The output also keeps lua syntax and the script can easily be modified for simple persistent storage by writing the output to file if modified to allow only number  boolean  string and table data types to be formatted   function print table node      local cache  stack  output                local depth   1     local output str      n       while true do         local size   0         for k v in pairs node  do             size   size   1         end          local cur index   1         for k v in pairs node  do             if  cache node     nil  or  cur index  gt   cache node   then                  if  string find output str     output str len     then                     output str   output str       n                  elseif not  string find output str   n  output str len     then                     output str   output str      n                  end                  -- This is necessary for working with HUGE tables otherwise we run out of memory using concat on huge strings                 table insert output output str                  output str                       local key                 if  type k      number  or type k      boolean   then                     key        tostring k                       else                     key         tostring k                        end                  if  type v      number  or type v      boolean   then                     output str   output str    string rep   t  depth     key           tostring v                  elseif  type v      table   then                     output str   output str    string rep   t  depth     key          n                      table insert stack node                      table insert stack v                      cache node    cur index 1                     break                 else                     output str   output str    string rep   t  depth     key            tostring v                       end                  if  cur index    size  then                     output str   output str      n     string rep   t  depth-1                         else                     output str   output str                        end             else                 -- close the table                 if  cur index    size  then                     output str   output str      n     string rep   t  depth-1                         end             end              cur index   cur index   1         end          if  size    0  then             output str   output str      n     string rep   t  depth-1                 end          if   stack  gt  0  then             node   stack  stack              stack  stack    nil             depth   cache node     nil and depth   1 or depth - 1         else             break         end     end      -- This is necessary for working with HUGE tables otherwise we run out of memory using concat on huge strings     table insert output output str      output str   table concat output       print output str  end   Here is an example   local t           abe      1 2 3 4 5        string1       50        depth1         depth2         depth3         depth4         depth5         depth6         depth7        depth8         depth9         depth10      1000   900   800  700  600  500   400    300   200   100         ted      true false  some text         string2        function   return end    function   return end      75    print table t    Output          1     string1        2    50       3     string2        4    75        abe                1    1           2    2           3    3           4    4           5    5              function  06472B70      function  06472A98         depth1                1    100            depth2                    1    200                depth3                        1    300                    depth4                            1    400                        depth5                                1    500                            depth6                                    1    600                                depth7                                        1    700                                    depth8                                            1    800                                        depth9                                                1    900                                            depth10                                                    1    1000                                                                                                                                                                                                                                                        ted                1    true           2    false           3     some text

User · Answer

The table tostring metehod of metalua is actually very complete  It deals with nested tables  the indentation level is changeable      See https   github com fab13n metalua blob master src lib metalua table2 lua

User · Answer

This is my version that supports excluding tables and userdata  -- Lua Table View by Elertan table print   function t  exclusions      local nests   0     if not exclusions then exclusions      end     local recurse   function t  recurse  exclusions          indent   function               for i   1  nests do                 io write                     end         end         local excluded   function key              for k v in pairs exclusions  do                 if v    key then                     return true                 end             end             return false         end         local isFirst   true         for k v in pairs t  do             if isFirst then                 indent                   print                      isFirst   false             end             if type v      table  and not excluded k  then                 indent                   print   - gt     k        type v                   nests   nests   1                 recurse v  recurse  exclusions              elseif excluded k  then                 indent                   print   - gt     k        type v               elseif type v      userdata  or type v      function  then                 indent                   print   - gt     k        type v               elseif type v      string  then                 indent                   print   - gt     k              v                    else                 indent                   print   - gt     k        v              end         end         nests   nests - 1     end      nests   0     print      START TABLE           for k v in pairs t  do         print  root           if type v      table  then             print   - gt     k        type v               nests   nests   1             recurse v  recurse  exclusions          elseif type v      userdata  or type v      function  then             print   - gt     k        type v           elseif type v      string  then             print   - gt     k              v                else             print   - gt     k        v          end     end     print      END TABLE       end   This is an example  t         location            x   10         y   20            size           width   100000000        height   1000             name    Sidney       test             hi    lol              anotherone             1           2           3          table print t     test       Prints          START TABLE     root  - gt  size  table            - gt  height  1000      - gt  width  100000000 root  - gt  location  table            - gt  y  20      - gt  x  10 root  - gt  anotherone  table            - gt  1  1      - gt  2  2      - gt  3  3 root  - gt  test  table            - gt  hi   lol  root  - gt  name   Sidney      END TABLE       Notice that the root doesn t remove exclusions

User · Answer

As previously mentioned  you have to write it  Here is my humble version   super basic one   function tprint  t  s      for k  v in pairs t  do         local kfmt           tostring k                 if type k      string  then             kfmt          k                end         local vfmt         tostring v                if type v      table  then             tprint v   s or      kfmt          else             if type v      string  then                 vfmt   tostring v              end             print type t    s or      kfmt         vfmt          end     end end   example   local mytbl       1    a   2  3  b  c   t  d 1    tprint mytbl    output  Lua 5 0    table 1    2 table 2    3 table  1      a  table  t    d     1 table  b      c

User · Answer

Format as JSON  you can  beautify  in IDE later    local function format any value obj  buffer      local  type   type obj      if  type     table  then         buffer  buffer   1                 for key  value in next  obj  nil do             buffer  buffer   1    tostring key                      format any value value  buffer              buffer  buffer   1                 end         buffer  buffer        -- note the overwrite     elseif  type     string  then         buffer  buffer   1           obj            elseif  type     boolean  or  type     number  then         buffer  buffer   1    tostring obj      else         buffer  buffer   1               type               end end   Usage   local function format as json obj      if obj    nil then return  null  else         local buffer              format any value obj  buffer          return table concat buffer      end end  local function print as json obj      print  format as json obj   end  print as json  1  2  3  print as json nil  print as json  string   print as json   1    1   2    2  three       true      four    four     BTW  I also wrote several other solutions  a very fast one  and one with special characters escaping  https   github com vn971 fast json encode

User · Answer

You have to code it yourself I m afraid  I wrote this  and it may be of some use to you  function printtable table  indent     indent   indent or 0     local keys          for k in pairs table  do     keys  keys 1    k      table sort keys  function a  b        local ta  tb   type a   type b         if  ta    tb  then         return ta  lt  tb        else         return a  lt  b        end     end     end    print string rep       indent           indent   indent   1    for k  v in pairs table  do      local key   k      if  type key      string   then       if not  string match key     A-Za-z   0-9A-Za-z        then         key         key              end     elseif  type key      number   then       key        key           end      if  type v      table   then       if  next v   then         printf   s s     string rep       indent   tostring key            printtable v  indent         else         printf   s s         string rep       indent   tostring key          end      elseif  type v      string   then       printf   s s    s    string rep       indent   tostring key        v            else       printf   s s    s    string rep       indent   tostring key   tostring v        end   end   indent   indent - 1    print string rep       indent         end

User · Answer

I use my own function to print the contents of a table but not sure how well it translates to your environment  ---A helper function to print a table s contents  --- param tbl table  The table to print  --- param depth number  The depth of sub-tables to traverse through and print  --- param n number  Do NOT manually set this  This controls formatting through recursion  function PrintTable tbl  depth  n    n   n or 0    depth   depth or 5     if  depth    0  then       print string rep      n    quot     quot          return    end    if  n    0  then       print  quot   quot      end    for key  value in pairs tbl  do       if  key and type key      quot number quot  or type key      quot string quot   then           key   string format  quot    quot  s  quot   quot   key              if  type value      quot table quot   then               if  next value   then                   print string rep      n   key   quot      quot                      PrintTable value  depth - 1  n   4                     print string rep      n    quot    quot                  else                   print string rep      n   key   quot        quot                  end           else               if  type value      quot string quot   then                   value   string format  quot   quot  s  quot  quot   value                 else                   value   tostring value                 end                print string rep      n   key   quot     quot   value   quot   quot              end       end   end    if  n    0  then       print  quot   quot      end end

User · Answer

I have humbly modified a bit Alundaio code   -- by Alundaio -- KK modified 11 28 2019  function dump table to string node  tree  indentation      local cache  stack  output                local depth   1       if type node      table  then         return  only table type is supported  got      type node      end      if nil    indentation then indentation   1 end      local NEW LINE     n      local TAB CHAR            if nil    tree then         NEW LINE     n      elseif not tree then         NEW LINE              TAB CHAR          end      local output str          NEW LINE      while true do         local size   0         for k v in pairs node  do             size   size   1         end          local cur index   1         for k v in pairs node  do             if  cache node     nil  or  cur index  gt   cache node   then                  if  string find output str     output str len     then                     output str   output str           NEW LINE                 elseif not  string find output str NEW LINE output str len     then                     output str   output str    NEW LINE                 end                  -- This is necessary for working with HUGE tables otherwise we run out of memory using concat on huge strings                 table insert output output str                  output str                       local key                 if  type k      number  or type k      boolean   then                     key        tostring k                       else                     key         tostring k                        end                  if  type v      number  or type v      boolean   then                     output str   output str    string rep TAB CHAR depth indentation     key           tostring v                  elseif  type v      table   then                     output str   output str    string rep TAB CHAR depth indentation     key              NEW LINE                     table insert stack node                      table insert stack v                      cache node    cur index 1                     break                 else                     output str   output str    string rep TAB CHAR depth indentation     key            tostring v                       end                  if  cur index    size  then                     output str   output str    NEW LINE    string rep TAB CHAR  depth-1  indentation                         else                     output str   output str                        end             else                 -- close the table                 if  cur index    size  then                     output str   output str    NEW LINE    string rep TAB CHAR  depth-1  indentation                         end             end              cur index   cur index   1         end          if  size    0  then             output str   output str    NEW LINE    string rep TAB CHAR  depth-1  indentation                 end          if   stack  gt  0  then             node   stack  stack              stack  stack    nil             depth   cache node     nil and depth   1 or depth - 1         else             break         end     end      -- This is necessary for working with HUGE tables otherwise we run out of memory using concat on huge strings     table insert output output str      output str   table concat output       return output str  end   then   print dump table to string  AA   true 3    print dump table to string   AA   BB    true 3    print dump table to string   AA   BB      print dump table to string   AA   BB   false    print dump table to string   AA   BB   22 33   true 2     gives   only table type is supported  got string        1     AA       2     BB         1     AA     2     BB       1     AA   2     BB         1     AA      2     BB      3           1    22       2    33

User · Answer

I know this question has already been marked as answered  but let me plug my own library here  It s called inspect lua  and you can find it here   https   github com kikito inspect lua  It s just a single file that you can require from any other file  It returns a function that transforms any Lua value into a human-readable string   local inspect   require  inspect    print inspect  1 2 3    --  1  2  3  print inspect  a 1 b 2   --   --   a   1 --   b   2 --     It indents subtables properly  and handles  recursive tables   tables that contain references to themselves  correctly  so it doesn t get into infinite loops  It sorts values in a sensible way  It also prints metatable information   Regards

User · Answer

I ve found this one useful   Because if the recursion it can print nested tables too   It doesn t give the prettiest formatting in the output but for such a simple function it s hard to beat for debugging   function dump o     if type o      table  then       local s              for k v in pairs o  do          if type k      number  then k        k      end          s   s         k            dump v               end       return s            else       return tostring o     end end   e g   local people                name    Fred         address    16 Long Street         phone    123456                    name    Wilma         address    16 Long Street         phone    123456                    name    Barney         address    17 Long Street         phone    123457           print  People    dump people     Produces the following output      People       1        address     16 Long Street   phone       123456   name     Fred     2        address     16 Long   Street   phone     123456   name     Wilma     3        address     17   Long Street   phone     123457   name     Barney

User · Answer

Adding another version  This one tries to iterate over userdata as well   function inspect o indent      if indent    nil then indent   0 end     local indent str   string rep         indent      local output it   function str          print indent str  str      end      local length   0      local fu   function k  v          length   length   1         if type v      userdata  or type v      table  then             output it indent str       k                   inspect v  indent 1          else             output it indent str       k        tostring v           end     end      local loop pairs   function           for k v in pairs o  do fu k v  end     end      local loop metatable pairs   function           for k v in pairs getmetatable o   do fu k v  end     end      if not pcall loop pairs  and not pcall loop metatable pairs  then         output it indent str                else         if length    0 then             output it indent str                end     end end

User · Answer

found this   -- Print contents of  tbl   with indentation  --  indent  sets the initial level of indentation  function tprint  tbl  indent    if not indent then indent   0 end   for k  v in pairs tbl  do     formatting   string rep       indent     k             if type v      table  then       print formatting        tprint v  indent 1      elseif type v      boolean  then       print formatting    tostring v             else       print formatting    v      end   end end   from here https   gist github com ripter 4270799  works pretty good for me

[lua] How to dump a table to console?

Examples related to lua