Maximum Length of Command Line String

Question

In Windows  what is the maximum length of a command line string  Meaning if I specify a program which takes arguments on the command line such as abc exe -name abc   A simple console application I wrote takes parameters via command line and I want to know what is the maximum allowable amount

User · Accepted Answer

From the Microsoft documentation  Command prompt  Cmd  exe  command-line string limitation     On computers running Microsoft Windows XP or later  the maximum length of the string that you can use at the command prompt is 8191 characters

User · Answer

Sorry for digging out an old thread  but I think sunetos  answer isn t correct  or isn t the full answer   I ve done some experiments  using ProcessStartInfo in c   and it seems that the  arguments  string for a commandline command is limited to 2048 characters in XP and 32768 characters in Win7  I m not sure what the 8191 limit refers to  but I haven t found any evidence of it yet

User · Answer

As  Sugrue I m also digging out an old thread   To explain why there is 32768  I think it should be 32767  but lets believe experimental testing result  characters limitation we need to dig into Windows API   No matter how you launch program with command line arguments it goes to ShellExecute  CreateProcess or any extended their version  These APIs basically wrap other NT level API that are not officially documented  As far as I know these calls wrap NtCreateProcess  which requires OBJECT ATTRIBUTES structure as a parameter  to create that structure InitializeObjectAttributes is used  In this place we see UNICODE STRING  So now lets take a look into this structure   typedef struct  UNICODE STRING       USHORT Length      USHORT MaximumLength      PWSTR  Buffer    UNICODE STRING    It uses USHORT  16-bit length  0  65535   variable to store length  And according this  length indicates size in bytes  not characters  So we have  65535   2   32767  because WCHAR is 2 bytes long    There are a few steps to dig into this number  but I hope it is clear     Also  to support  sunetos answer what is accepted  8191 is a maximum number allowed to be entered into cmd exe  if you exceed this limit  The input line is too long  error is generated  So  answer is correct despite the fact that cmd exe is not the only way to pass arguments for new process

User · Answer

In Windows 10  it s still 8191 characters   at least on my machine   It just cuts off any text after 8191 characters  Well  actually  I got 8196 characters  and after 8196  then it just won t let me type any more   Here s a script that will test how long of a statement you can use  Well  assuming you have gawk awk installed   echo rem this is a test of how long of a line that a  cmd script can generate  gt testbat bat gawk  BEGIN  printf  echo -----  for  i 10 i  lt  100000 i   10  printf    06d----  i print print  pause      gt  gt testbat bat testbat bat

[windows] Maximum Length of Command Line String

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