New -n option for read builtin

Usage: read -n nchars
Reads maximum of nchars characters. If nchars <= 0, there's no limit.

1 files changed, 53 insertions, 3 deletions

diff --git a/builtin.cpp b/builtin.cpp
index da9429b1..cde4477f 100644
--- a/builtin.cpp
+++ b/builtin.cpp
@@ -2313,6 +2313,8 @@ static int builtin_read(parser_t &parser, wchar_t **argv)
     const wchar_t *commandline = L"";
     int exit_res=STATUS_BUILTIN_OK;
     const wchar_t *mode_name = READ_MODE_NAME;
+    int nchars=0;
+    wchar_t *end;
     int shell = 0;
     int array = 0;
 
@@ -2356,6 +2358,10 @@ static int builtin_read(parser_t &parser, wchar_t **argv)
             }
             ,
             {
+                L"nchars", required_argument, 0, 'n'
+            }
+            ,
+            {
                 L"shell", no_argument, 0, 's'
             }
             ,
@@ -2377,7 +2383,7 @@ static int builtin_read(parser_t &parser, wchar_t **argv)
 
         int opt = wgetopt_long(argc,
                                argv,
-                               L"xglUup:c:hm:sa",
+                               L"xglUup:c:hm:n:sa",
                                long_options,
                                &opt_index);
         if (opt == -1)
@@ -2428,6 +2434,32 @@ static int builtin_read(parser_t &parser, wchar_t **argv)
                 mode_name = woptarg;
                 break;
 
+            case L'n':
+                errno = 0;
+                nchars = fish_wcstoi(woptarg, &end, 10);
+                if (errno || *end != 0)
+                {
+                    switch (errno)
+                    {
+                        case ERANGE:
+                            append_format(stderr_buffer,
+                                    _(L"%ls: Argument '%ls' is out of range\n"),
+                                    argv[0],
+                                    woptarg);
+                            builtin_print_help(parser, argv[0], stderr_buffer);
+                            return STATUS_BUILTIN_ERROR;
+
+                        default:
+                            append_format(stderr_buffer,
+                                    _(L"%ls: Argument '%ls' must be an integer\n"),
+                                    argv[0],
+                                    woptarg);
+                            builtin_print_help(parser, argv[0], stderr_buffer);
+                            return STATUS_BUILTIN_ERROR;
+                    }
+                }
+                break;
+
             case 's':
                 shell = 1;
                 break;
@@ -2530,11 +2562,24 @@ static int builtin_read(parser_t &parser, wchar_t **argv)
         proc_push_interactive(1);
 
         event_fire_generic(L"fish_prompt");
-        line = reader_readline();
+        line = reader_readline(nchars);
         proc_pop_interactive();
         if (line)
         {
-            buff = wcsdup(line);
+            if (0 < nchars && nchars < wcslen(line))
+            {
+                // line may be longer than nchars if a keybinding used `commandline -i`
+                // note: we're deliberately throwing away the tail of the commandline.
+                // It shouldn't be unread because it was produced with `commandline -i`,
+                // not typed.
+                buff = (wchar_t *)malloc(((size_t)nchars + 1) * sizeof(wchar_t));
+                wmemcpy(buff, line, (size_t)nchars);
+                buff[nchars] = 0;
+            }
+            else
+            {
+                buff = wcsdup(line);
+            }
         }
         else
         {
@@ -2594,6 +2639,11 @@ static int builtin_read(parser_t &parser, wchar_t **argv)
                 break;
 
             sb.push_back(res);
+
+            if (0 < nchars && (size_t)nchars <= sb.size())
+            {
+                break;
+            }
         }
 
         if (sb.size() < 2 && eof)