argv

问题 if(strcmp(argv[2], NULL) == 0) I'm passing 3 command line arguments but I also want to run it with only 2 command line arguments with the above statement. But a segmentation fault error is being displayed. I also tried with if(argc < 3) but it also didn't work...same segmentation fault... 回答1: Why segmentation fault? Because of code if(strcmp(argv[2], NULL) == 0) , you are passing NULL as string pointer to strcmp() function; that try to deference at NULL to compare chars codes (e.g. acsii

问题 I'm getting a segmentation fault for the following code. Can somebody explain why? I would like to be able to copy the contents of argv into a new array, which I called rArray. #include <iostream> using namespace std; int main( int argc, char **argv) { char **rArray; int numRows = argc; cout << "You have " << argc << " arguments:" << endl << endl; cout << "ARGV ARRAY" << endl; for (int i = 0; i < argc; i++) { cout << argv[i] << endl; } cout << endl << endl << "COPIED ARRAY" << endl; for(int i

问题 I have a C program that reads command line arguments from argv. Is it possible to make a pipe to redirect the contents of a file as command line arguments to my program? Suppose I have a file arguments.dat with this content: 0 0.2 302 0 And I want my program to be called with: ./myprogram 0 0.2 302 0 I tried the following: cat arguments.dat | ./myprogram without success. 回答1: With most shells, you can insert the contents of a file into a command line with $(<filename) : ./myprogram $(

问题 This question already has answers here : Closed 6 years ago . Possible Duplicate: About command line arguments of main function How would I determine what the maximum size of data I could pass into a C main(int argc, char* argv)? Is there a macro somewhere in the standard that would define this? Is the data "owned" by the main process (i.e. does my program store this data) or is it somehow "owned" by the operating system and I can just get a pointer to it? 回答1: In a POSIX system, there is a

问题 I'm making a small program in C that deals with a lot of command line arguments, so I decided to use getopt to sort them for me. However, I want two non-option arguments (source and destination files) to be mandatory, so you have to have them as arguments while calling the program, even if there's no flags or other arguments. Here's a simplified version of what I have to handle the arguments with flags: while ((c = getopt(argc, argv, "i:d:btw:h:s:")) != -1) { switch (c) { case 'i': { i = (int

问题 I Learn Python From "Learn Python the Hard way" I don't know what is argv !! (please explain argv with Example and text) Question 2: What is Different between raw_input & argv ? 回答1: argv stands for arg ument v alue and it represents the arguments passed to your program when it is launched from the command line. For example, if your program is called example.py , and you run it like this: $ example.py 'hello' Then argv is hello . raw_input is a way to prompt the user for some input. Basically

问题 I am writing a program in C that spawns loads of processes and that should report their state via argv[0] so while calling ps it's easy to see what's going on. I am aware that initially argv[0] comes with certain memory allocated, that contains the program name (in most cases). I need however to set much longer string than 20 bytes that contain my program name. My status can be 80-100 characters long. I made some tests and if I memcpy this longer string into argv[0] it "works for me" but I am

问题 This question already has answers here : Reading fractions in C (6 answers) Closed 5 years ago . I need to add fractions given by the user through command prompt in the format a/b b/c I thought I could do it this way: n1 = atoi(argv[1]); d1 = atoi(argv[3]); n2 = atoi(argv[4]); d2 = atoi(argv[6]); Thereby skipping the slashes, but this just crashes the program. Is there some way to skip over certain characters passed as arguments through command prompt? Thank you in advance. 回答1: If the user

问题 I am currently using ARGV.gets to capture user input from the command line. I want to allow Ctrl-D terminate the script, but don't know how to do this using Signal.trap or through error handling. I tried to find a list of trap codes for something like Ctrl-D but was unable to find anything I was looking for. Likewise, rescuing Exception doesn't work because Ctrl-D doesn't raise an exception. Is there a trap code for Ctrl-D or any other way to detect this? For example... I am currently able to

问题 very basic question. i try to write a program that outputs the filenames of the files dragged onto the exe. i followed this guide for main arguments: http://publications.gbdirect.co.uk/c_book/chapter10/arguments_to_main.html this is my code: #include "stdafx.h" #include <iostream> using namespace std; int _tmain(int argc, _TCHAR* argv[]) { cout<<"num arguments: "<<argc<<"\n"; while(argc--) printf("%s\n", *argv++); cout<<"press any key"; getchar(); return 0; } but all it output's is: if i run