getline

问题 Is there an easy way to check if a line is empty. So i want to check if it contains any white space such as \r\n\t and spaces. Thanks 回答1: You can use the isspace function in a loop to check if all characters are whitespace: int is_empty(const char *s) { while (*s != '\0') { if (!isspace((unsigned char)*s)) return 0; s++; } return 1; } This function will return 0 if any character is not whitespace (i.e. line is not empty), or 1 otherwise. 回答2: If a string s consists only of white space

问题 I want to have my program open a text file, go down to a specific line (for example, line 18) and store each character on that line in a char vector. I'm fairly new to programming in general so this may not be the best way but here's what I plan on doing: 1) Get specific line and store it in a string 2) Convert that string to a char vector. I'm using a vector instead of an array so I can use pushback() to make the vector the exact size needed instead of allocating too much or too little in an

问题 I'm trying to read lines from .txt files, that have been saved as Unicode. That's how i'm doing it: wifstream input; string path = "test.txt"; input.imbue(locale(input.getloc(), new codecvt_utf16<wchar_t, 0x10ffff, consume_header>)); input.open(path); if (input.is_open()) { wstring line; input.seekg( 1 , ios_base::beg); getline(input, line); } It works fine for files with Latin characters. But for Cyrillic files I get weird symbols instead of spaces and adjacent characters. For example: What

问题 Data saved in my file is (white spaces added at both beginning and end on purpose for this test): 1 2 3 Loading the data using the code below with or without "std::ws" does not cause any difference. So I am confused by the role of "std::ws" as I have seen code using it. Can someone explain a little bit? Thanks! void main () { ifstream inf; inf.open ("test.txt"); double x=0, y=0, z=0; string line; getline(inf, line); istringstream iss(line); //Using "std::ws" here does NOT cause any difference

问题 What I want is to get the reversed string of current line, I tried to use the rev command in the AWK but cannot get the current result. $ cat myfile.txt abcde $ cat myfile.txt | awk '{cmd="echo "$0"|rev"; cmd | getline result; print "result="$result; close(cmd);}' abcde I want to get edcba in the output. I know there are some other ways to get the reversed string like $ cat myfile.txt | exec 'rev' . Using AWK here is because there are some other processes to do. Did I miss anything? 回答1: The

问题 What I want is to get the reversed string of current line, I tried to use the rev command in the AWK but cannot get the current result. $ cat myfile.txt abcde $ cat myfile.txt | awk '{cmd="echo "$0"|rev"; cmd | getline result; print "result="$result; close(cmd);}' abcde I want to get edcba in the output. I know there are some other ways to get the reversed string like $ cat myfile.txt | exec 'rev' . Using AWK here is because there are some other processes to do. Did I miss anything? 回答1: The

问题 I have a theoretical question: 1) How pass a variable to the system of getline ()? awk 'BEGIN{var="ls"; var | getline var; system("echo $var")}' 2) How to assign a variable the output system ("ls") and print the result in awk? awk 'BEGIN{var="system("ls")"; print '$var'}' 3) Can you assign a variable in the system (var = "ls") and print the result in awk? awk 'BEGIN{system(var="ls"); print "'"$var"'"}' Thank you for the information. EDIT: torek : Thank you for your response. I understand that

问题 I have a theoretical question: 1) How pass a variable to the system of getline ()? awk 'BEGIN{var="ls"; var | getline var; system("echo $var")}' 2) How to assign a variable the output system ("ls") and print the result in awk? awk 'BEGIN{var="system("ls")"; print '$var'}' 3) Can you assign a variable in the system (var = "ls") and print the result in awk? awk 'BEGIN{system(var="ls"); print "'"$var"'"}' Thank you for the information. EDIT: torek : Thank you for your response. I understand that

问题 I want to write a C program that takes a simple math problem from the user and use different processes to solve each part, and then send the value back to the parent process. This program should not pay attention to the order of operations. For instance, if I have the problem: 3 + 4 / 7 + 4 * 2 I want my program to output the following: Enter problem: 3 + 4 / 7 + 4 * 2 PID 20419 calculated 3+4 as 7 PID 20420 calculated 7/7 as 1 PID 20421 calculated 1+4 as 5 PID 20422 calculated 5*2 as 10

问题 I'm trying to read in a CSV file that contains rows of 3 people/patients, where col 1 is userid, col 2 is fname, col 3 is lname, col 4 is insurance, and col 5 is version that looks something like below. Edit: Apologies, I simply copy/pasted my CSV spreadsheet in here, so it didn't show the commas before. Wouldn't it look something more like below? John below also pointed out that there are no commas after the version, and this seemed to fix the issue! Thanks so much John! ( trying to figure