Author [email protected]
Date Aug. 15, 2023
Description libreadline-dev介绍和例子
简介
在实现一个类shell的程序的时候,可能需要使用到命令补全以及命令历史记录。这时候就可以使用libreadline库,这是一个GNU开发的库,官网是:The GNU Readline Library。
这个库主要提供命令补全、命令修改以及命令历史,当然命令历史有一个单独的库叫做History library,但这里就一起装一起用了,而且包管理器也没有区分(apt show libreadline-dev
可以查看依赖包)。
当然最好的教程就是官网的文档。第一部分算是介绍,第二部分是开发,上面也给了很多例子,可以直接照抄了。
安装
- apt系:
sudo apt install libreadline-dev
- yum系:
sudo yum install readline-devel
- 源码:没试过,下面是我猜测的,不过GNU的源码安装都基本是同样命令
git clone git://git.savannah.gnu.org/readline.git ./configure make sudo make install sudo ldconfig
使用
它主要有两个头文件,<readline/readline.h>
和<readline/history.h>
,前者就是命令行编辑、命令补全等,后者就是命令历史。如果要查看所有的头文件,那就去/usr/include/readline/
下查看。
默认情况下,readline只提供对文件名的补全。这个例子介绍了下,主要就两个函数:
readline(prompt_string)
:获取用户输入,可以补全文件名add_history(input_string)
:用户输入加入历史,可以使用上下箭头进行切换。
但是使用readline一般是为了自定义命令。这个例子的源码在GNU Readline Library的教程库中,叫做fileman.c。我重新整理了下这个例子,原来的函数参数写法好像是C标准还没有成立时的写法,不过无所谓了,是能看懂的。
在这个例子中,其实主要还是看readline相关的函数吧,其它的再学习。例子中,定义了一个COMMAND数据结构,然后定义了该数据结构的数组,描述各个命令、执行函数以及对应含义。在这个例子中和readline相关:
- 一个是
add_history
,就是把命令加入历史记录。 - 一个是
rl_attempted_completion_function
,这是一个指针变量,指向命令补全的函数,这个函数fileman_completion
中text就是用户已输入,start和end为在rl_line_buffer中的边界。start不一定为0,那是因为命令补全不一定是从第一个单词开始的。例如ls bu
,要补全为build,那么start就是3,end是5。 - 一个是
rl_completion_matches
,创建matches,相当于是返回的是所有匹配的命令以及文件。如果没有输入,就返回所有的命令了;部分输入有匹配返回匹配,没有匹配返回NULL。 - 当然还有一堆的执行函数,以
com_
开头,那就是具体的命令的逻辑了。
简单编译使用
gcc -o fileman fileman.c -I/usr/include/readline -lreadline
更多功能还是参考官网文档吧。
- GNU Readline Library
- The GNU Readline Library
- The GNU History Library
- The GNU Readline User Interface
源码
<details> <summary>fileman.c整理后的源码</summary>
/* readline exmaple code getting from
* https://tiswww.case.edu/php/chet/readline/readline.html#A-Short-Completion-Example
*/
/* fileman.c -- A tiny application which demonstrates how to use the
* GNU Readline library. This application interactively allows users
* to manipulate files and their modes. */
#include <sys/types.h>
#include <sys/file.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>
#include <errno.h>
#include <locale.h>
#include <string.h>
#include <stdlib.h>
#include <time.h>
#include <readline/readline.h>
#include <readline/history.h>
/* The name of this program, as taken from argv[0]. */
static char *progname;
/* When non-zero, this global means the user is done using this program. */
static int done;
/* String to pass to system (). This is for the LIST, VIEW and RENAME
* commands. */
static char syscom[1024];
/* The names of functions that actually do the manipulation. */
int com_list(char *);
int com_view(char *);
int com_rename(char *);
int com_stat(char *);
int com_pwd(char *);
int com_delete(char *);
int com_help(char *);
int com_cd(char *);
int com_quit(char *);
/* A structure which contains information on the commands this program
* can understand. */
typedef struct {
char *name; /* User printable name of the function. */
rl_icpfunc_t *func; /* Function to call to do the job. */
char *doc; /* Documentation for this function. */
} COMMAND;
/* commands array */
COMMAND commands[] = {
{ "cd", com_cd, "Change to directory DIR" },
{ "delete", com_delete, "Delete FILE" },
{ "help", com_help, "Display this text" },
{ "?", com_help, "Synonym for `help'" },
{ "list", com_list, "List files in DIR" },
{ "ls", com_list, "Synonym for `list'" },
{ "pwd", com_pwd, "Print the current working directory" },
{ "quit", com_quit, "Quit using Fileman" },
{ "rename", com_rename, "Rename FILE to NEWNAME" },
{ "stat", com_stat, "Print out statistics on FILE" },
{ "view", com_view, "View the contents of FILE" },
{ (char *)NULL, (rl_icpfunc_t *)NULL, (char *)NULL }
};
/* Look up NAME as the name of a command, and return a pointer to that
* command. Return a NULL pointer if NAME isn't a command name. */
COMMAND* find_command (char *name)
{
register int i;
for (i = 0; commands[i].name; i++)
if (strcmp (name, commands[i].name) == 0)
return (&commands[i]);
return ((COMMAND *)NULL);
}
/* Execute a command line. */
int execute_line (char *line)
{
register int i;
COMMAND *command;
char *word;
/* Isolate the command word. */
i = 0;
while (line[i] && whitespace (line[i]))
i++;
word = line + i;
while (line[i] && !whitespace (line[i]))
i++;
if (line[i])
line[i++] = '\0';
command = find_command (word);
if (!command)
{
fprintf (stderr, "%s: No such command for FileMan.\n", word);
return (-1);
}
/* Get argument to command, if any. */
while (whitespace (line[i]))
i++;
word = line + i;
/* Call the function. */
return ((*(command->func)) (word));
}
/* Strip whitespace from the start and end of STRING. Return a pointer
* into STRING. */
char* stripwhite (char *string)
{
register char *s, *t;
for (s = string; whitespace (*s); s++)
;
if (*s == 0)
return (s);
t = s + strlen (s) - 1;
while (t > s && whitespace (*t))
t--;
*++t = '\0';
return s;
}
/* Function which tells you that you can't do this. */
void too_dangerous (char *caller)
{
fprintf (stderr,
"%s: Too dangerous for me to distribute. Write it yourself.\n",
caller);
}
/* **************************************************************** */
/* */
/* Interface to Readline Completion */
/* */
/* **************************************************************** */
/* Generator function for command completion. STATE lets us know whether
* to start from scratch; without any state (i.e. STATE == 0), then we
* start at the top of the list. */
char * command_generator (const char *text, int state)
{
static int list_index, len;
char *name;
/* If this is a new word to complete, initialize now. This includes
* saving the length of TEXT for efficiency, and initializing the index
* variable to 0. */
if (!state)
{
list_index = 0;
len = strlen (text);
}
/* Return the next name which partially matches from the command list. */
while ((name = commands[list_index].name))
{
list_index++;
if (strncmp (name, text, len) == 0)
return (strdup(name));
}
/* If no names matched, then return NULL. */
return ((char *)NULL);
}
/* Attempt to complete on the contents of TEXT. START and END bound the
* region of rl_line_buffer that contains the word to complete. TEXT is
* the word to complete. We can use the entire contents of rl_line_buffer
* in case we want to do some simple parsing. Return the array of matches,
* or NULL if there aren't any. */
char **fileman_completion (const char *text, int start, int end)
{
char **matches;
matches = (char **)NULL;
/* If this word is at the start of the line, then it is a command
* to complete. Otherwise it is the name of a file in the current
* directory. */
if (start == 0)
matches = rl_completion_matches (text, command_generator);
return (matches);
}
/* Tell the GNU Readline library how to complete. We want to try to complete
* on command names if this is the first word in the line, or on filenames
* if not. */
void initialize_readline ()
{
/* Allow conditional parsing of the ~/.inputrc file. */
rl_readline_name = "FileMan";
/* Tell the completer that we want a crack first. */
rl_attempted_completion_function = fileman_completion;
}
/* Return non-zero if ARG is a valid argument for CALLER, else print
* an error message and return zero. */
int valid_argument (char *caller, char *arg)
{
if (!arg || !*arg)
{
fprintf (stderr, "%s: Argument required.\n", caller);
return (0);
}
return (1);
}
/* **************************************************************** */
/* */
/* FileMan Commands */
/* */
/* **************************************************************** */
/* List the file(s) named in arg. */
int com_list (char *arg)
{
if (!arg)
arg = "";
sprintf (syscom, "ls -FClg %s", arg);
return (system (syscom));
}
int com_view (char *arg)
{
if (!valid_argument ("view", arg))
return 1;
#if defined (__MSDOS__)
/* more.com doesn't grok slashes in pathnames */
sprintf (syscom, "less %s", arg);
#else
sprintf (syscom, "more %s", arg);
#endif
return (system (syscom));
}
int com_rename (char *arg)
{
too_dangerous ("rename");
return (1);
}
int com_stat (char *arg)
{
struct stat finfo;
if (!valid_argument ("stat", arg))
return (1);
if (stat (arg, &finfo) == -1)
{
perror (arg);
return (1);
}
printf ("Statistics for `%s':\n", arg);
printf ("%s has %ld link%s, and is %ld byte%s in length.\n",
arg,
finfo.st_nlink,
(finfo.st_nlink == 1) ? "" : "s",
finfo.st_size,
(finfo.st_size == 1) ? "" : "s");
printf ("Inode Last Change at: %s", ctime (&finfo.st_ctime));
printf (" Last access at: %s", ctime (&finfo.st_atime));
printf (" Last modified at: %s", ctime (&finfo.st_mtime));
return (0);
}
int com_delete (char *arg)
{
too_dangerous ("delete");
return (1);
}
/* Print out help for ARG, or for all of the commands if ARG is
* not present. */
int com_help (char *arg)
{
register int i;
int printed = 0;
for (i = 0; commands[i].name; i++)
{
if (!*arg || (strcmp (arg, commands[i].name) == 0))
{
printf ("%s\t\t%s.\n", commands[i].name, commands[i].doc);
printed++;
}
}
if (!printed)
{
printf ("No commands match `%s'. Possibilities are:\n", arg);
for (i = 0; commands[i].name; i++)
{
/* Print in six columns. */
if (printed == 6)
{
printed = 0;
printf ("\n");
}
printf ("%s\t", commands[i].name);
printed++;
}
if (printed)
printf ("\n");
}
return (0);
}
/* Change to the directory ARG. */
int com_cd (char *arg)
{
if (chdir (arg) == -1)
{
perror (arg);
return 1;
}
com_pwd ("");
return (0);
}
/* Print out the current working directory. */
int com_pwd (char *ignore)
{
char dir[1024], *s;
s = getcwd (dir, sizeof(dir) - 1);
if (s == 0)
{
printf ("Error getting pwd: %s\n", dir);
return 1;
}
printf ("Current directory is %s\n", dir);
return 0;
}
/* The user wishes to quit using this program. Just set DONE non-zero. */
int com_quit (char *arg)
{
done = 1;
return (0);
}
int main (int argc, char **argv)
{
char *line, *s;
setlocale (LC_ALL, "");
progname = argv[0];
initialize_readline (); /* Bind our completer. */
/* Loop reading and executing lines until the user quits. */
for ( ; done == 0; )
{
line = readline ("FileMan: ");
if (!line)
break;
/* Remove leading and trailing whitespace from the line.
* Then, if there is anything left, add it to the history list
* and execute it. */
s = stripwhite (line);
if (*s)
{
add_history (s);
execute_line (s);
}
free (line);
}
exit (0);
}
</details>
标签:return,libreadline,dev,char,int,例子,arg,line,com From: https://blog.51cto.com/basilguo/7090426