getchar_unlocked - Linux


getchar_unlocked is a C library function used for retrieving a single character from the standard input. It is primarily utilized in low-level input handling, especially when immediate and efficient character retrieval is required.


#include <stdio.h>
int getchar_unlocked(void);


getchar_unlocked does not take any options or flags.


Simple Input Handling:

int ch;
while ((ch = getchar_unlocked()) != EOF) {

Custom Input Validation:

int ch;
while ((ch = getchar_unlocked()) != EOF) {
  if (isalpha(ch)) {
    // Process alphabetic character

Common Issues

Blocking Input:
getchar_unlocked blocks execution until a character is entered. This behavior can be problematic if you need to handle input from multiple sources or want to avoid blocking the thread.

Non-canonical Input:
getchar_unlocked reads characters in non-canonical mode, meaning it does not wait for a newline character to be entered. If you need to read a line of input, consider using fgets or getline.


Command Pipeline:
getchar_unlocked can be combined with other Linux commands using pipes to create versatile input handling pipelines:

command1 | grep "pattern" | getchar_unlocked

Command Substitution:
getchar_unlocked can be used in command substitution to capture user input and pass it as an argument to another command:

echo "Your name:"

Related Commands

  • getchar: Similar to getchar_unlocked but blocks in canonical mode.
  • fgets: Reads a line of input from standard input.
  • getline: Similar to fgets but allows for more advanced input handling.