Date: 5 Oct 2000 12:58:02 -0000 From: "Peter Pentchev" <roam@orbitel.bg> To: FreeBSD-gnats-submit@freebsd.org Subject: bin/21766: [PATCH] add -s (skip) flag to head(1) Message-ID: <20001005125802.7108.qmail@ringwraith.office1>
next in thread | raw e-mail | index | archive | help
>Number: 21766
>Category: bin
>Synopsis: [PATCH] add -s (skip) flag to head(1)
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: change-request
>Submitter-Id: current-users
>Arrival-Date: Thu Oct 05 06:00:04 PDT 2000
>Closed-Date:
>Last-Modified:
>Originator: "Peter Pentchev" <roam@orbitel.bg>
>Release: FreeBSD 4.1.1-STABLE i386
>Organization:
Orbitell JSCo.
>Environment:
FreeBSD 4.1.1-STABLE #1: Thu Oct 5 13:13:32 EEST 2000
>Description:
It is sometimes useful to display, say, the *second* 20 lines of a file.
Yes, I am perfectly aware that head -40 | tail -20 works, but having
head(1) able to skip lines/bytes is a little bit better in my book :)
The attached patch adds a -s flag, expecting a numeric argument; that
number of lines/bytes is skipped, after which the quantity requested
by -n or -c (or the implicit 10) are displayed as usual.
>How-To-Repeat:
Try to display the second 20 (or 800 in my case) lines of a file;
watch yourself go through loops ;)
>Fix:
diff -urN src/usr.bin/head/head.1 mysrc/usr.bin/head/head.1
--- src/usr.bin/head/head.1 Sat Aug 28 04:01:58 1999
+++ mysrc/usr.bin/head/head.1 Thu Oct 5 15:43:08 2000
@@ -42,6 +42,7 @@
.Nm head
.Op Fl n Ar count
.Op Fl c Ar bytes
+.Op Fl s Ar skipcount
.Op Ar file ...
.Sh DESCRIPTION
This filter displays the first
@@ -60,6 +61,14 @@
where
.Dq XXX
is the name of the file.
+.Pp
+If
+.Ar skipcount
+is specified, the
+.Nm head
+utility skips the specified number of lines or bytes before displaying
+the requested
+.Ar count .
.Pp
The
.Nm head
diff -urN src/usr.bin/head/head.c mysrc/usr.bin/head/head.c
--- src/usr.bin/head/head.c Sat Aug 28 04:01:58 1999
+++ mysrc/usr.bin/head/head.c Thu Oct 5 15:37:31 2000
@@ -60,8 +60,8 @@
* Bill Joy UCB August 24, 1977
*/
-void head __P((FILE *, int));
-void head_bytes __P((FILE *, int));
+void head __P((FILE *, int, int));
+void head_bytes __P((FILE *, int, int));
void obsolete __P((char *[]));
void usage __P((void));
@@ -74,11 +74,11 @@
{
register int ch;
FILE *fp;
- int first, linecnt = -1, bytecnt = -1;
+ int first, linecnt = -1, bytecnt = -1, skipcnt = 0;
char *ep;
obsolete(argv);
- while ((ch = getopt(argc, argv, "n:c:")) != -1)
+ while ((ch = getopt(argc, argv, "n:c:s:")) != -1)
switch(ch) {
case 'c':
bytecnt = strtol(optarg, &ep, 10);
@@ -90,6 +90,11 @@
if (*ep || linecnt <= 0)
errx(1, "illegal line count -- %s", optarg);
break;
+ case 's':
+ skipcnt = strtol(optarg, &ep, 10);
+ if (*ep || skipcnt <= 0)
+ errx(1, "illegal skip count -- %s", optarg);
+ break;
case '?':
default:
usage();
@@ -113,40 +118,49 @@
first ? "" : "\n", *argv);
first = 0;
}
- if (bytecnt == -1)
- head(fp, linecnt);
- else
- head_bytes(fp, bytecnt);
+ if (bytecnt == -1) {
+ if (skipcnt) head(fp, skipcnt, 0);
+ head(fp, linecnt, 1);
+ } else {
+ if (skipcnt) head_bytes(fp, skipcnt, 0);
+ head_bytes(fp, bytecnt, 1);
+ }
(void)fclose(fp);
}
}
- else if (bytecnt == -1)
- head(stdin, linecnt);
- else
- head_bytes(stdin, bytecnt);
+ else if (bytecnt == -1) {
+ if (skipcnt) head(stdin, skipcnt, 0);
+ head(stdin, linecnt, 1);
+ } else {
+ if (skipcnt) head_bytes(stdin, skipcnt, 0);
+ head_bytes(stdin, bytecnt, 1);
+ }
exit(eval);
}
void
-head(fp, cnt)
+head(fp, cnt, out)
FILE *fp;
register int cnt;
+ int out;
{
register int ch;
while (cnt && (ch = getc(fp)) != EOF) {
+ if (out)
if (putchar(ch) == EOF)
err(1, "stdout");
- if (ch == '\n')
- cnt--;
- }
+ if (ch == '\n')
+ cnt--;
+ }
}
void
-head_bytes(fp, cnt)
+head_bytes(fp, cnt, out)
FILE *fp;
register int cnt;
+ int out;
{
char buf[4096];
register int readlen;
@@ -159,8 +173,9 @@
readlen = fread(buf, sizeof(char), readlen, fp);
if (readlen == 0)
break;
- if (fwrite(buf, sizeof(char), readlen, stdout) != readlen)
- err(1, "stdout");
+ if (out)
+ if (fwrite(buf, sizeof(char), readlen, stdout) != readlen)
+ err(1, "stdout");
cnt -= readlen;
}
}
>Release-Note:
>Audit-Trail:
>Unformatted:
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-bugs" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20001005125802.7108.qmail>