fgets

How to read and overwrite text file in C?

由 ﹥＞﹥吖頭↗ 提交于 2019-12-05 04:47:17
I have a text file text.txt that reads (for simplicity purposes) this is line one this is line two this is line three Again for simplicity's sake, I am just trying to set the first character in each line to 'x', so my desired result would be xhis is line one xhis is line two xhis is line three So I am opening the text.txt file and trying to overwrite each line with the desired output to the same text file. In the while loop, I set the first character in each line to 'x'. I also set the variable "line" equal to one, because if its on the first line, I want to rewind to the beginning of the file

C++: Store read binary file into buffer

由 谁都会走 提交于 2019-12-04 22:52:56
问题 I'm trying to read a binary file and store it in a buffer. The problem is, that in the binary file are multiple null-terminated characters, but they are not at the end, instead they are before other binary text, so if I store the text after the '\0' it just deletes it in the buffer. Example: char * a = "this is a\0 test"; cout << a; This will just output: this is a here's my real code: this function reads one character bool CStream::Read (int * _OutChar) { if (!bInitialized) return false; int

What does fgets do?

由 Deadly 提交于 2019-12-04 21:23:12
It is not equal: fgets (answer, 256, stdin); if (strncmp(answer, "sta", 4) == 0) printf("omg, it's equal"); This code is: fgets (answer, 4, stdin); if (strncmp(answer, "sta", 4) == 0) printf("omg, it's equal"); Why? It is because in the first, answer doesn't have \0 at the 4th place I guess (if I change it to 3 instead of 4 it works). But what does fgets do? String answer in the first is str \whitespace*253\0" ? And in the second it is str\0 ? Thank you. fgets (unlike gets ) includes the trailing \n corresponding to the return pressed at the end of the line. If you put 3 as the limit it

ARTS Week 3

由 杀马特。学长 韩版系。学妹 提交于 2019-12-04 18:59:12
Nov 11,2019 ~ Nov 17,2019 Algorithm 本周来介绍快速求一个数字n次方的余数。 理论基础 我们先定义运算$ x \bmod p = r $与$ x \equiv r \pmod p $的含义是一样的。若$ p = 5 $，则可以将所有整数划分到5个不相交的集合里，具体如下： $$ \left{\begin{matrix} & {\dots -10, -5, 0, 5, 10 \dots } \bmod 5 = 0 & \ & {\dots -9, -4, 1, 6, 11 \dots } \bmod 5 = 1 & \ & {\dots -8, -3, 2, 7, 12 \dots } \bmod 5 = 2 & \ & {\dots -7, -2, 3, 8, 13 \dots } \bmod 5 = 3 & \ & {\dots -6, -1, 4, 9, 14 \dots } \bmod 5 = 4 & \ \end{matrix}\right. $$ 可能有人不懂为什么$-4 \bmod 5 = 1$，我来解释一下，因为$ -4 = 5 \times (-1) + 1 $，故$ -4 \div 5 = -0.8 = -1 \cdots 1 $。因此$-4 \bmod 5 = 1$ 那么根据上面的描述

fgets is getting skipped

由 孤者浪人 提交于 2019-12-04 05:25:48
问题 I have little program where I want to ask for an option and then for a filename. //Some code before printf("######################\n"); printf("# 1. Register a file #\n"); printf("# 2. Get global list #\n"); printf("# 3. Download a file #\n"); printf("# 4. Quit / Exit #\n"); printf("######################\n"); printf("Enter decision: "); fflush(stdin); action = getchar(); action -= '0'; sprintf(input, "[%d]--", action); switch (action) { case 1: printf("Enter file name: "); fflush(stdin);

Does fgets() always null-terminate the string it returns?

由 喜欢而已 提交于 2019-12-04 04:59:27
问题 Is this safe to do? Does fgets terminate the buffer with null or should I be setting the 20th byte to null after the call to fgets and before I call clean ? // strip new lines void clean(char *data) { while (*data) { if (*data == '\n' || *data == '\r') *data = '\0'; data++; } } // for this, assume that the file contains 1 line no longer than 19 bytes // buffer is freed elsewhere char *load_latest_info(char *file) { FILE *f; char *buffer = (char*) malloc(20); if (f = fopen(file, "r")) if

Ignoring whitepace with fscanf or fgets?

由 守給你的承諾、 提交于 2019-12-04 04:24:44
问题 I was wondering if there is any way to ignore whitespace with either the fscanf or fgets function. My text file has two chars on each line that may or may not be separated by a space. I need to read the two chars and place each one in a different array. file = fopen(argv[1], "r"); if ((file = fopen(argv[1], "r")) == NULL) { printf("\nError opening file"); } while (fscanf(file, "%s", str) != EOF) { printf("\n%s", str); vertexArray[i].label = str[0]; dirc[i] = str[1]; i += 1; } 回答1: Using a

C, how to use fgets and fscanf together

由 烂漫一生 提交于 2019-12-04 02:13:14
问题 i hav a homework form univ. that is use file IO. there is like this TXT file: Brian s213551 50 70 70 50 Alex Fernandes s210011 70 81 50 89 Young Lee s211213 60 80 60 90 ... and more I have to read this file and save to var in struct. and prof. said to me. I have to use fgets and fscanf together. if I use only fscanf its not working nicely because "Alex Fernandes" has space in it. but even though I use fgets and fscanf together, its not working.. so i need help u. this is my source: #include

fgets adds \0 or \n at the end of the input?

由 柔情痞子 提交于 2019-12-03 22:47:59
问题 I've some doubts about fgets. From what I know, it adds "\n" at the end of the string, and not "\0". So if I write this code: fgets(buff,2,stdin); printf("%s",buff); So fgets reads two characters, I give as input "y", so buff should be "y\n". I'd expect printf to print y and add a line, while it prints "y" without adding a line. Can you explain why? 回答1: char * fgets ( char * str, int num, FILE * stream ); Reads characters from input stream and stores them as a C string into str until (num-1)

Segmentation fault in fgets() - C language

由 一世执手 提交于 2019-12-03 20:32:56
I am getting a segmentation fault exactly at this line: while (fgets(line, MAX_LEN + 1, stream) != NULL) { .... } where MAX_LEN is 500, line is reading the current line, and stream is open through fopen(filename, "r"); I am reading lines from a file with a specific format and I get a segmentation fault (Core dumps) exactly at this line according to the debugger. I made my code so that it ignores lines that do not match the scanf format. Here is what I am implementing. Something close to it at least: int main(int argc, int **argv) { .... .... if (argc == 1) { printf("enter file name: "); scanf(
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