Read History

Task

Implement the function read_history

• Open a file in read mode, read all lines, and print each with a line number (starting from 1)
• If fopen() fails, call perror("open") and return -1
• If successful, return 0

Format: line_number command space between number and command

Function Signature

// Read history file and print each line with line number.
// Format: "1 command"
// Return 0 on success, -1 on error.
int read_history(const char* filepath);

Important File I/O functions

• fopen(filename, "r")→ Open file in read mode
• fgets(buffer, size, file) → Read line from file
• fclose(file) → Close the file

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Example

$ gcc read_history.c -o read_history
$ echo -e "ls -l\npwd\necho hello" > test.txt
$ ./read_history
test.txt
1 ls -l
2 pwd
3 echo hello
$ ./read_history
/nonexistent.txt
open: No such file or directory

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Code

#include <stdio.h>
 
int read_history(const char *filepath)
{
    FILE* file = fopen(filepath, "r");
    if(file == NULL){
        perror("open");
        return -1;
    }
 
    char buffer[100];
    int i = 1;
    while(fgets(buffer, sizeof(buffer), file) != NULL){
        printf("%d %s", i, buffer);
        i++;
    }
 
    fclose(file);
    return 0;
}