During Turbo c2.0 startup, three parameters of the main () function are passed: argc, argv, and Env.
* Argc: the number of main () command line parameters.
* Argv: String Array.
Argv [0] indicates the full path name of the program.
Argv [1] is the first string after the program name is executed in the doscommand line;
Argv [2] is the second string after the execution program name;
...
Argv [argc] is null.
* Env: String Array. Each element of env [] contains characters in the form of envvar = value.
String. Envvar is the environment variable. Value is the corresponding value of envvar.
# Include <stdlib. h>
# Include <stdio. h> main (INT argc, char * argv [], char * env []) {
Int I;
Printf ("% d/N", argc);/* Why is its output 1? What is it defined? I don't understand the above explanation */
For (I = 0; I <= argc; I ++)
Printf ("argv [% d]: % s/n", I, argv [I]);
For (I = 0; ENV [I]! = NULL; I ++)
Printf ("env [% d]: % s/n", I, ENV [I]);} argc, argv, ENV are assigned values before the main () function, the executable file generated by the compiler. Main () is not a real entry point, but a standard function. The function name is related to the specific operating system.
Printf ("% d/N", argc) // output 1 is correct because the executable file name is the first parameter, that is, argv [0] = number of executable file names argc containing command line options, argv contains argc C-style strings, indicates the Command Options separated by spaces. For example, if you enter the name of the executable program, work.exe follows-d-o ....
Then argv [0] = work.exe argv [1] =-D argv [2] =-o
You can let them output it to an example:
# Include <stdio. h>;Int main (INT argc, char * argv [])
{
Printf ("% d/N", argc );
While (argc)
Printf ("% s/n", argv [-- argc]);
Return 0;
} Compile it as test.exe,
Under the command line,
Test hello
The output result is
2
Hello
Test Main (INT argc, char * argv []), where argc refers to the number of variables. In this example, it refers to test and hello, that is, 2,
The argc must be at least 1. I don't need to say that.
Argv is an array of char *, which stores the content of the variable.
The example of storing test and argv [1] In argv [0] is really classic, so it is left behind. It is useful for understanding the argv [] function. |
