X-Git-Url: https://git.subgeniuskitty.com/unix-history/.git/blobdiff_plain/2b84abb596f52ab2068d52108adc96838ad4340a..31cef89cb428866f787983e68246030321893df4:/usr/src/cmd/tail.c

diff --git a/usr/src/cmd/tail.c b/usr/src/cmd/tail.c
index 9ef7b41774..e298f8440a 100644
--- a/usr/src/cmd/tail.c
+++ b/usr/src/cmd/tail.c
@@ -1,3 +1,4 @@
+static char *sccsid = "@(#)tail.c	4.1 (Berkeley) 10/6/80";
 /* tail command 
  *
  *	tail where [file]
@@ -6,14 +7,23 @@
  *	+ means nth line from beginning
  *	type 'b' means tail n blocks, not lines
  *	type 'c' means tail n characters
+ *	Type 'r' means in lines in reverse order from end
+ *	 (for -r, default is entire buffer )
+ *	option 'f' means loop endlessly trying to read more
+ *		characters after the end of file, on the  assumption
+ *		that the file is growing
 */
+
+#include	<stdio.h>
+#include	<ctype.h>
 #include	<sys/types.h>
 #include	<sys/stat.h>
 #include	<errno.h>
-#include	<pagsiz.h>
-#define	BUFSIZ	BSIZE
+
 #define LBIN 4097
 struct	stat	statb;
+int	follow;
+int	piped;
 char bin[LBIN];
 int errno;
 
@@ -21,11 +31,11 @@ main(argc,argv)
 char **argv;
 {
 	long n,di;
-	int fromend;
 	register i,j,k;
+	char	*arg;
+	int partial,bylines,bkwds,fromend,lastnl;
 	char *p;
-	int partial,piped,bylines;
-	char *arg;
+
 	lseek(0,(long)0,1);
 	piped = errno==ESPIPE;
 	arg = argv[1];
@@ -36,36 +46,48 @@ char **argv;
 	}
 	fromend = *arg=='-';
 	arg++;
-	if(!digit(*arg))
-		goto errcom;
 	n = 0;
-	while(digit(*arg))
+	while(isdigit(*arg))
 		n = n*10 + *arg++ - '0';
 	if(!fromend&&n>0)
 		n--;
 	if(argc>2) {
 		close(0);
 		if(open(argv[2],0)!=0) {
-			write(2,"tail: can't open ",17);
-			write(2,argv[2],strlen(argv[2]));
-			write(2,"\n",1);
+			perror(argv[2]);
 			exit(1);
 		}
 	}
-	bylines = 0;
-	switch(*arg) {
+	bylines = -1; bkwds = 0;
+	while(*arg)
+	switch(*arg++) {
+
 	case 'b':
 		n <<= 9;
+		if(bylines!=-1) goto errcom;
+		bylines=0;
 		break;
 	case 'c':
+		if(bylines!=-1) goto errcom;
+		bylines=0;
+		break;
+	case 'f':
+		follow = 1;
+		break;
+	case 'r':
+		if(n==0) n = LBIN;
+		bkwds = 1; fromend = 1; bylines = 1;
 		break;
-	case '\0':
 	case 'l':
+		if(bylines!=-1) goto errcom;
 		bylines = 1;
 		break;
 	default:
 		goto errcom;
 	}
+	if (n==0) n = 10;
+	if(bylines==-1) bylines = 1;
+	if(bkwds) follow=0;
 	if(fromend)
 		goto keep;
 
@@ -78,7 +100,8 @@ char **argv;
 				if(j--<=0) {
 					p = bin;
 					j = read(0,p,BUFSIZ);
-					if(j--<=0) exit(0);
+					if(j--<=0)
+						fexit();
 				}
 			} while(*p++ != '\n');
 		}
@@ -90,25 +113,30 @@ char **argv;
 			while(n>0) {
 				i = n>BUFSIZ?BUFSIZ:n;
 				i = read(0,bin,i);
-				if(i<=0) exit(0);
+				if(i<=0)
+					fexit();
 				n -= i;
 			}
 		else
 			lseek(0,n,0);
 	}
+copy:
 	while((i=read(0,bin,BUFSIZ))>0)
 		write(1,bin,i);
-	exit(0);
+	fexit();
 
 			/*seek from end*/
 
 keep:
-	if(n<=0) exit(0);
+	if(n <= 0)
+		fexit();
 	if(!piped) {
 		fstat(0,&statb);
 		di = !bylines&&n<LBIN?n:LBIN-1;
 		if(statb.st_size > di)
 			lseek(0,-di,2);
+		if(!bylines)
+			goto copy;
 	}
 	partial = 1;
 	for(;;) {
@@ -130,18 +158,33 @@ brka:
 		    i-n+LBIN;
 		k--;
 	} else {
+		if(bkwds && bin[i==0?LBIN-1:i-1]!='\n'){	/* force trailing newline */
+			bin[i]='\n';
+			if(++i>=LBIN) {i = 0; partial = 0;}
+		}
 		k = i;
 		j = 0;
 		do {
+			lastnl = k;
 			do {
 				if(--k<0) {
-					if(partial)
+					if(partial) {
+						if(bkwds) write(1,bin,lastnl+1);
 						goto brkb;
+					}
 					k = LBIN -1;
 				}
 			} while(bin[k]!='\n'&&k!=i);
+			if(bkwds && j>0){
+				if(k<lastnl) write(1,&bin[k+1],lastnl-k);
+				else {
+					write(1,&bin[k+1],LBIN-k-1);
+					write(1,bin,lastnl+1);
+				}
+			}
 		} while(j++<n&&k!=i);
 brkb:
+		if(bkwds) exit(0);
 		if(k==i) do {
 			if(++k>=LBIN)
 				k = 0;
@@ -153,13 +196,18 @@ brkb:
 		write(1,&bin[k+1],LBIN-k-1);
 		write(1,bin,i);
 	}
-	exit(0);
+	fexit();
 errcom:
-	write(2,"usage: tail +_n[lbc] [file]\n",29);
-	exit(1);
+	fprintf(stderr, "usage: tail [+_[n][lbc][rf]] [file]\n");
+	exit(2);
 }
 
-digit(c)
-{
-	return(c>='0'&&c<='9');
+fexit()
+{	register int n;
+	if (!follow || piped) exit(0);
+	for (;;)
+	{	sleep(1);
+		while ((n = read (0, bin, BUFSIZ)) > 0)
+			write (1, bin, n);
+	}
 }