UNIX Shell and History Feature - linux

Question

how to add History Feature in unix shell to allows the user to access the most recently entered
command , The user will be able to access up to 10 commands by using the
feature.
This comment explain the history part from the project:
The user will be able to access up to 10 commands by using the
feature. The commands will be consecutively numbered starting at 1, and
the numbering will continue past 10. For example, if the user has entered 35
commands, the 10 most recent commands will be numbered 26 to 35.
The userwill be able to list the command history by entering the command
history
at the osh> prompt. As an example, assume that the history consists of the
commands (from most to least recent):
ps, ls -l, top, cal, who, date
The command history will output:
6 ps
5 ls -l
4 top
3 cal
2 who
1 date
Your program should support two techniques for retrieving commands
from the command history:
1. When the user enters !!, the most recent command in the history is
executed.
2. When the user enters a single ! followed by an integer N, the Nth
command in the history is executed.
this is my code that including the history part, but i have error and dont know how to fix it. please help
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#define MAX_LINE 80
char *history[10][MAX_LINE];
int po;
void setup(char inputBuffer[], char *args[],int *background)
{
int length,
i,
start,
ct;
ct = 0;
length = read(STDIN_FILENO, inputBuffer, MAX_LINE);
start = -1;
if (length == 0)
exit(0);
if (length < 0){
perror("error ");
exit(-1);
}
for (i = 0; i < length; i++) {
switch (inputBuffer[i]){
case ' ':
case '\t' :
if(start != -1){
args[ct] = &inputBuffer[start];
ct++;
}
inputBuffer[i] = '\0';
start = -1;
break;
case '\n':
if (start != -1){
args[ct] = &inputBuffer[start];
ct++;
}
inputBuffer[i] = '\0';
args[ct] = NULL;
break;
case '&':
*background = 1;
inputBuffer[i] = '\0';
break;
default :
if (start == -1)
start = i;
}
}
args[ct] = NULL;
}
int main(void)
{
char inputBuffer[MAX_LINE];
int background;
char *args[MAX_LINE/2+1];
while (1){
background = 0;
printf("os>");
fflush(0);
setup(inputBuffer, args, &background);
/**
* After reading user input, the steps are:
* (1) fork a child process using fork()
* (2) the child process will invoke execvp()
* (3) if command included &, parent will invoke wait()
*/
pid_t pid = fork();
printf("Fork created.\n");
/*
For example, if the
user enters the command ps -ael at the osh> prompt, the values stored in the
args array are:
args[0] = "ps"
args[1] = "-ael"
args[2] = NULL
This args array will be passed to the execvp() function, which has the
following prototype:
execvp(char *command, char *params[]);
*/
if(pid < 0){
printf("Fork failed.\n");
}else if(pid == 0){
if( strcmp(args[0],"history") == 0){ /* Print History */
displayHistory();
}else if(strcmp(args[0],"r") == 0){ /* r num */
int index = (int) args[1];
/*runHistoryAt( index - 1);*/
}else if(strcmp(args[0],"rr") == 0){ /* Run recent */
/*runHistoryAt(0);*/
}else{ /* Execute normally */
printf("executing..., adding to history buffer\n");
/* Add args to history buffer */
int j;
for (j = 0; j < sizeof(args); j++) {
history[po][j] = args[j];
}
po = (po + 1) % 10;
/* Execute! */
execvp(args[0],args);
}
}
if(background == 0){
wait(NULL);
}else{
setup(inputBuffer, args, &background);
}
}
}

Answer 1

I would use the GNU readline library. It gives you line edition and history support and you can also have completion.