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Questions tagged [stdio]

This tag is for questions regarding "Standard I/O", i.e. I/O using the facilities in the C header or using the standard streams stdin, stdout, stderr.

The C standard header <stdio.h> defines facilities for using data streams via FILE objects and also declares the pre-defined standard streams, stdin, stdout and stderr.

The standard IO streams can be used from C in two ways:

  1. Using standard IO streams as implemented by the standard header <stdio.h> e.g. fprintf (stdout, "hello, world\n");
  2. Using the underlying file descriptors directly using the facilities in <unistd.h> e.g. write (STDOUT_FILENO, "hello, world\n", 13);. Note that this is not ISO C, but POSIX.
1090 questions
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Why does the terminal hang when reading from STDOUT?

So I've entered two lines of code into a Python shell to read from STDOUT and write to STDIN: >>> writetoinput=open("/dev/stdin","w") >>> readfromoutput=open("/dev/stdout") and unexpected things happen when you do file operations on them. First, I…
The Empty String Photographer
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What if I put 2 or more into 'size' parameter in fread()?

If I use: fread(&buffer, 16384, 1, file); // Read 16384 bytes once? instead of: fread(&buffer, 1, 16384, file); // Read a byte 16384 times? to read a plain text document file, would it succeed? Is it efficient?
user11140649
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How to remove the final "%" sign from the output in c with printf()

I have the following code: #include int main(){ printf("hello world"); } The output is the following: hello world% Is there a way to remove the final "%" (which is actually black on white and not white on black like the other…
ecjb
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Having infinite loop because scanf() does not stop the program to take entry from user

I need to write a program which calculates fibonacci sequence but I stuck because of this infinite loop. When I enter -5 it prints Please enter "positive" term(s) number:. Then I enter "a" and it prints Please enter "numeric" term(s) number:…
Baran
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Broken files in C

I made a simple script to rewrite one file contents into another. Here's code: #include #include int main() { char filename[1024]; scanf("%s", &filename); // printf("Filename: '%s'\n", filename); int…
Зелди
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How to write a c program that takes 2 strings as arguments from the command line?

I want to write a .c program using only libraries stdlib.h, stdio.h, and string.h. The program takes as input from the command line two words when the C program is is called - like this: .mycode WORD1 WORD2 where WORD1 and WORD2 are both series of…
prince12
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My code gives out Environment variables on Linux

Some of this code might not make any sense, (perhaps even I am perplexed) about how this happened and why? This code was intended for some other purpose, (i was trying to make a calculator, so the main source code [which had few problems] exists…
Sparsh_Mishra
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C++ How can I redirect STDIN to a function

I've spent some time researching for a way to redirect STDOUT and STDIN to functions. While I eventually found and succeeded at redirecting STDOUT to a callback, I'm unable to redirect STDIN to a callback too (I can't find any resources except for…
Ricardo Antunes
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Error in stdio.h file?

I'm trying to write and run "Hello World" in C. int main(int argc, char *argv[]) { #include puts("Hello world."); return 0; } However, I keep getting the following error in the Terminal: In file included from…
maloneet198
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Whatever input, the answer is 67 ,why?

#include #include int main() { int a; scanf("%*2s",&a); printf("%d\n",a); return 0; } Output: 1351 (input to scanf) 67 (output from printf) Whatever input I give,the answer is always 67. Where is the 67 coming…
JingYi
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fastest way to write integer to file in C

I am doing a homework to programming in C. Bonus points are for quick writing to the file in there upload test system. I am trying to write a number of lines each comprising three space delimited decimal integer strings and then '\n' in file. The…
Stepan
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Having issues with C using float and printf

I'm trying to run some basic code in C to declare 2 float variables, and then divide them and put that value in the 3rd variable. After this I print all 3. #include int main () { /* variable definition: */ float a, b, c; /* variable…
Rick Hammer
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Find Quantity of Biggest integers in N integers in C

I want to do this code that tells you the number of (n) integers that are bigger (or equal) than a (k) input. So for example: input: 4 15 12 6 15 24 output: 2 So the 4 is the number of integers the user is going to input and the 15 is the k…
Redspark77
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Not able to get particluar sequence in C but am able to get it in Python

I am trying to get a very simple and basic logic up and running using the C language. The following code gets it right on python, but I am not able to get the same results using C. //Python Code a = 2 while True: a=a*2 print(a) With the…
Vishal Subramanyam
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Search file and compare strings it contains with inputted variable

I'm trying to search a file containing information on a group of people, for example: their first name, last name and ID. I'm prompting the user to enter their ID code. The program should search the text file and ensure that their code matches the…
Keneil Ricketts
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