Re: [patch] vcs.4: broken example code

[Mattias Engdegård <mattiase@xxxxxxx>]

Ping. (Michael Witten wanted to update the page text but let's at least
fix the example code first.)

Fix broken example code in the vcs.4 man page
- use of wrong variable (attrib, which is uninitialised, instead of s)
- variable ch too narrow
- printing a font char index with %c, as if it were ASCII (it's not)
- removing the high font bit while changing the background colour
- unwarranted assumption of little-endian byte order

Also be friendly and use SEEK_* instead of numbers.
---
 man4/vcs.4 | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/man4/vcs.4 b/man4/vcs.4
index aebe8cfda..f695b956c 100644
--- a/man4/vcs.4
+++ b/man4/vcs.4
@@ -140,7 +140,8 @@ main(void)
     struct {unsigned char lines, cols, x, y;} scrn;
     unsigned short s;
     unsigned short mask;
-    unsigned char ch, attrib;
+    unsigned char attrib;
+    int ch;
 
     fd = open(console, O_RDWR);
     if (fd < 0) {
@@ -158,16 +159,16 @@ main(void)
         exit(EXIT_FAILURE);
     }
     (void) read(fd, &scrn, 4);
-    (void) lseek(fd, 4 + 2*(scrn.y*scrn.cols + scrn.x), 0);
+    (void) lseek(fd, 4 + 2*(scrn.y*scrn.cols + scrn.x), SEEK_SET);
     (void) read(fd, &s, 2);
     ch = s & 0xff;
-    if (attrib & mask)
+    if (s & mask)
         ch |= 0x100;
     attrib = ((s & ~mask) >> 8);
-    printf("ch=\(aq%c\(aq attrib=0x%02x\\n", ch, attrib);
-    attrib ^= 0x10;
-    (void) lseek(fd, \-1, 1);
-    (void) write(fd, &attrib, 1);
+    printf("ch=0x%03x attrib=0x%02x\\n", ch, attrib);
+    s ^= 0x1000;
+    (void) lseek(fd, \-2, SEEK_CUR);
+    (void) write(fd, &s, 2);
     exit(EXIT_SUCCESS);
 }
 .EE