Re: let head(1) understand `-' as stdin

[Jan Stary]

On Oct 11 21:27:54, j...@wxcvbn.org wrote:
> Jan Stary <h...@stare.cz> writes:
> 
> > The diff below makes head(1) recognize `-'
> > as a name for the standard input,
> > as many other utilities do.
> 
> Makes sense to me.  The following points could be improved IMO:

Updated diff below.

> - using strcmp sounds cleaner than those char comparisons

OK

> - I don't think the man page bits are needed.  Utilities that read from
>   stdin are supposed to support `-'.  I'm not sure whether the extra
>   example is really helpful.

I have removed the example.
I think the one sentence about "-" should stay;
other utils which recognize "-" mention it.

> - should we avoid closing stdin (multiple times)?

fixed


OK?


        Jan


Index: head.1
===================================================================
RCS file: /cvs/src/usr.bin/head/head.1,v
retrieving revision 1.23
diff -u -p -r1.23 head.1
--- head.1      25 Oct 2015 21:50:32 -0000      1.23
+++ head.1      11 Oct 2016 21:05:07 -0000
@@ -47,6 +47,9 @@ utility copies the first
 lines of each specified
 .Ar file
 to the standard output.
+A name of
+.Sq -
+is recognized as standard input.
 If no files are named,
 .Nm
 copies lines from the standard input.
Index: head.c
===================================================================
RCS file: /cvs/src/usr.bin/head/head.c,v
retrieving revision 1.21
diff -u -p -r1.21 head.c
--- head.c      20 Mar 2016 17:14:51 -0000      1.21
+++ head.c      11 Oct 2016 21:05:07 -0000
@@ -30,6 +30,7 @@
  */
 
 #include <stdio.h>
+#include <string.h>
 #include <stdlib.h>
 #include <ctype.h>
 #include <limits.h>
@@ -93,7 +94,8 @@ main(int argc, char *argv[])
                        if (pledge("stdio", NULL) == -1)
                                err(1, "pledge");
                } else {
-                       if ((fp = fopen(*argv, "r")) == NULL) {
+                       fp = strcmp(*argv, "-") ? fopen(*argv, "r") : stdin;
+                       if (fp == NULL) {
                                warn("%s", *argv++);
                                status = 1;
                                continue;
@@ -101,7 +103,8 @@ main(int argc, char *argv[])
                        if (argc > 1) {
                                if (!firsttime)
                                        putchar('\n');
-                               printf("==> %s <==\n", *argv);
+                               printf("==> %s <==\n",
+                                       fp == stdin ? "(stdin)" : *argv);
                        }
                        ++argv;
                }
@@ -109,7 +112,8 @@ main(int argc, char *argv[])
                        while ((ch = getc(fp)) != EOF)
                                if (putchar(ch) == '\n')
                                        break;
-               fclose(fp);
+               if (fp != stdin)
+                       fclose(fp);
        }
        /*NOTREACHED*/
 }