minishell-resources
FOR WAIT https://www.geeksforgeeks.org/wait-system-call-c/
The wait4() subroutine is similar to the wait3() subroutine except that we can specify the process ID of the child. The wait3() subroutine waits for any child process but the wait4() subroutine can wait for a specific child process.
FOR USING HISTORY
#include<stdio.h> #include<stdlib.h> #include<unistd.h> #include<readline/readline.h> #include<readline/history.h>
enum { MAXC = 128 };
int main (void){
char ps[MAXC] = "",
*p = getenv("USER"),
*host = getenv("HOSTNAME"),
*s = NULL;
int count = 1;
sprintf(ps, "%d %s@%s> ", count, p, host);
using_history(); /* initialize history */
while ((s = readline(ps))) {
if (strcmp (s, "quit") == 0) {
free (s);
break;
}
add_history (s);
free (s);
count++;
sprintf (ps, "%d %s@%s> ", count, p, host);
}
/* get the state of your history list (offset, length, size) */
HISTORY_STATE *myhist = history_get_history_state ();
FOR READLINE REDISPLAY
Function: int rl_redisplay ()
Function * rl redisplay function Variable
If non-zero, readline will call indirectly through this pointer to update the display with the current contents of the editing bu�er. By default, it is set to rl_redisplay, the default readline redisplay function (see Section 2.4.6 [Redisplay], page 24). int rl redisplay () Function Change what's displayed on the screen to reect the current contents of rl_ line_buffer. int rl forced upd
Function: int rl_on_new_line ()
Tell the update routines that we have moved onto a new (empty) line, usually after ouputting a newline.
Change what's displayed on the screen to reflect the current contents of rl_line_buffer
readline_clear_history
(PHP 4, PHP 5, PHP 7, PHP 8)
readline_clear_history — Clears the history
Description ¶ readline_clear_history(): bool This function clears the entire command line history.
Parameters ¶ This function has no parameters.
Return Values ¶ Returns true on success or false on failure.
＋add a note
Notes
./minishell goes to prompt for your shell using readline
add history stores history and automatically can use arrows to go back and forth.
write these built ins yourself
echo with -n option;
echo $? gives exit status of last closed process
echo $? +$?
0 + 0
cd with only a relative or absolute path;
(absolute path /bin
relative path bin)
cd . stays
cd .. goes one out
https://man7.org/linux/man-pages/man2/chdir.2.html
pwd;
export;
export inserts into env
export a = aaa
then a = aaa will be in env
if export a = aaa b = bbb
then
a =aaa
b = bbb
will be at end of env
unset;
unset removes from env
unset a
will remove it from env
both export and unset can do multiple variables and values
env;
env is our copy of env
exit;
(only one number acceptable to exit
exit means come out of shell)
crash = segfault
ctrl / dos nothing in parent but in child cat ^\ quit 3
child takes you out of shell
ctrl C returns prompt
if command then in child
when "" or '' acts as if a single command inside
when double quote
echo "$USER > name"
name
ie interpreted
when single quote
echo 'USER > name'
$USER
not interpreted
echo yes > a > b
yes will be in b . a will be created but empty
ls -la > a > c > d > e
only e will have ls -la in it
** order of options doesnt matter ls -la == ls -al
<< for here doc and followed by delimiter. Will print till delimiter
<<a
-> df
-> gh
-> a
df
gh
here delimiter is a so prints till a
/* retrieve the history list */ HIST_ENTRY **mylist = history_list ();
printf ("\nsession history for %s@%s\n\n", p, host);
for (int i = 0; i < myhist->length; i++) { /* output history list */
printf (" %8s %s\n", mylist[i]->line, mylist[i]->timestamp);
free_history_entry (mylist[i]); /* free allocated entries */
}
putchar ('\n');
free (myhist); /* free HIST_ENTRY list */
free (mylist); /* free HISTORY_STATE */
return 0;
} Example Use/Output
$ ./bin/readline
1 david@alchemy> command 1
2 david@alchemy> command 2
3 david@alchemy> command 3
4 david@alchemy> quit
session history for david@alchemy
command 1 command 2 command 3
FOR EXIT AND BONUS https://linuxize.com/post/bash-exit/
FOR && and || https://kyleshevlin.com/using-and-and-or-in-bash-scripts
https://man7.org/linux/man-pages/man3/getcwd.3.html https://man7.org/linux/man-pages/man2/ioctl.2.html https://man7.org/linux/man-pages/man2/chdir.2.html https://web.mit.edu/gnu/doc/html/rlman_2.html https://www.gnu.org/software/bash/manual/bash.html https://velog.io/@hidaehyunlee/minishell-2.-%ED%94%84%EB%A1%9C%EA%B7%B8%EB%9E%A8-%EA%B5%AC%EC%A1%B0-%EB%B0%8F-%EA%B0%9C%EB%B0%9C-%EA%B8%B0%EB%A1%9D%EB%93%A4 https://github.com/mharriso/school21-checklists/blob/master/ng_3_minishell.pdf https://www.youtube.com/watch?v=ubt-UjcQUYg https://www.cs.purdue.edu/homes/grr/SystemsProgrammingBook/Book/Chapter5-WritingYourOwnShell.pdf