The diff below makes head(1) recognize `-'
as a name for the standard input,
as many other utilities do.
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 13:33:23 -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.
@@ -77,6 +80,16 @@ To display the first 500 lines of the fi
.Ar foo :
.Pp
.Dl $ head -n 500 foo
+.Pp
+To display the first line of
+.Ar foo ,
+the standard input,
+.Ar bar
+and
+.Ar foo
+again:
+.Pp
+.Dl $ head -n 1 foo - bar foo
.Pp
.Nm
can be used in conjunction with
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 13:33:23 -0000
@@ -93,7 +93,9 @@ main(int argc, char *argv[])
if (pledge("stdio", NULL) == -1)
err(1, "pledge");
} else {
- if ((fp = fopen(*argv, "r")) == NULL) {
+ fp = (argv[0][0] == '-' && argv[0][1] == 0)
+ ? stdin : fopen(*argv, "r");
+ if (fp == NULL) {
warn("%s", *argv++);
status = 1;
continue;
@@ -101,7 +103,9 @@ main(int argc, char *argv[])
if (argc > 1) {
if (!firsttime)
putchar('\n');
- printf("==> %s <==\n", *argv);
+ printf("==> %s <==\n",
+ (argv[0][0] == '-' && argv[0][1] == 0)
+ ? "(stdin)" : *argv);
}
++argv;
}
