Parsing C++ Command-Line Arguments

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Microsoft Specific

Microsoft C/C++ startup code uses the following rules when interpreting arguments given on the operating system command line:

  • Arguments are delimited by white space, which is either a space or a tab.
  • The caret character (^) is not recognized as an escape character or delimiter. The character is handled completely by the command-line parser in the operating system before being passed to the argv array in the program.
  • A string surrounded by double quotation marks (« string« ) is interpreted as a single argument, regardless of white space contained within. A quoted string can be embedded in an argument.
  • A double quotation mark preceded by a backslash (« ) is interpreted as a literal double quotation mark character (« ).
  • Backslashes are interpreted literally, unless they immediately precede a double quotation mark.
  • If an even number of backslashes is followed by a double quotation mark, one backslash is placed in the argv array for every pair of backslashes, and the double quotation mark is interpreted as a string delimiter.
  • If an odd number of backslashes is followed by a double quotation mark, one backslash is placed in the argv array for every pair of backslashes, and the double quotation mark is « escaped » by the remaining backslash, causing a literal double quotation mark (« ) to be placed in argv.
Example

The following program demonstrates how command-line arguments are passed:

// command_line_arguments.cpp
// compile with: /EHsc
#include <iostream>

using namespace std;
int main( int argc,      // Number of strings in array argv
          char *argv[],   // Array of command-line argument strings
          char *envp[] )  // Array of environment variable strings
{
    int count;

    // Display each command-line argument.
    cout << "nCommand-line arguments:n";
    for( count = 0; count < argc; count++ )
         cout << "  argv[" << count << "]   "
                << argv[count] << "n";
}

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