commit 006c9739b3cff20a660fe15ffeb30be02a8fde5f
Author: FRIGN <[email protected]>
Date:   Mon Feb 9 18:38:41 2015 +0100

    Add c-flag to tail(1) and refactor manpage
    
    and mark it as finished in README.

diff --git a/README b/README
index 5fbaf06..ebd8120 100644
--- a/README
+++ b/README
@@ -64,7 +64,7 @@ The following tools are implemented ('*' == finished, '#' == 
UTF-8 support,
 =* sponge          non-posix                    none
    strings         no                           -a, -n, -t
 =* sync            non-posix                    none
-=  tail            no                           -c
+=* tail            yes                          none
 =* tar             non-posix                    none
 =* tee             yes                          none
    test            yes                          none
diff --git a/tail.1 b/tail.1
index 62df772..62a0df9 100644
--- a/tail.1
+++ b/tail.1
@@ -7,7 +7,7 @@
 .Sh SYNOPSIS
 .Nm
 .Op Fl f
-.Op Fl n Ar num
+.Op Fl c Ar num | Fl n Ar num
 .Op Ar file ...
 .Sh DESCRIPTION
 .Nm
@@ -20,19 +20,28 @@ is given,
 reads from stdin.
 .Sh OPTIONS
 .Bl -tag -width Ds
+.It Fl c Ar num | Fl n Ar num
+Display
+.Ar num
+last characters | lines. If
+.Ar num
+begins with '+' it is used as an offset from the beginning of each
+.Ar file .
+If
+.Ar num
+begins with '-' it is handled the same as if no sign was given.
 .It Fl f
 If one
 .Ar file
 is specified, append lines to output as
 .Ar file
 grows.
-.It Fl n Ar lines
-Display
-.Ar num
-lines. If
-.Ar num
-begins with '+' it is used as an offset from the beginning of each
-.Ar file .
 .El
 .Sh SEE ALSO
 .Xr head 1
+.Sh STANDARDS
+The
+.Nm
+utility is compliant with the
+.St -p1003.1-2008
+specification.
diff --git a/tail.c b/tail.c
index 984de9c..9893aad 100644
--- a/tail.c
+++ b/tail.c
@@ -9,43 +9,61 @@
 #include <unistd.h>
 
 #include "text.h"
+#include "utf.h"
 #include "util.h"
 
 static int fflag = 0;
 
 static void
-dropinit(FILE *fp, const char *str, size_t n)
+dropinit(FILE *fp, const char *str, size_t n, char mode)
 {
+       Rune r;
        char *buf = NULL;
        size_t size = 0, i = 0;
        ssize_t len;
 
-       while (i < n && (len = getline(&buf, &size, fp)) != -1)
-               if (len > 0 && buf[len - 1] == '\n')
+       if (mode == 'n') {
+               while (i < n && (len = getline(&buf, &size, fp)) != -1)
+                       if (len > 0 && buf[len - 1] == '\n')
+                               i++;
+       } else {
+               while (i < n && (len = readrune(str, fp, &r)))
                        i++;
+       }
        free(buf);
        concat(fp, str, stdout, "<stdout>");
 }
 
 static void
-taketail(FILE *fp, const char *str, size_t n)
+taketail(FILE *fp, const char *str, size_t n, char mode)
 {
+       Rune *r = NULL;
        char **ring = NULL;
        size_t i, j, *size = NULL;
 
-       ring = ecalloc(n, sizeof *ring);
-       size = ecalloc(n, sizeof *size);
+       if (mode == 'n') {
+               ring = ecalloc(n, sizeof *ring);
+               size = ecalloc(n, sizeof *size);
+
+               for (i = j = 0; getline(&ring[i], &size[i], fp) != -1; )
+                       i = j = (i + 1) % n;
+       } else {
+               r = ecalloc(n, sizeof *r);
 
-       for (i = j = 0; getline(&ring[i], &size[i], fp) != -1; )
-               i = j = (i + 1) % n;
+               for (i = j = 0; readrune(str, fp, &r[i]); )
+                       i = j = (i + 1) % n;
+       }
        if (ferror(fp))
                eprintf("%s: read error:", str);
 
        do {
-               if (ring[j]) {
+               if (ring && ring[j]) {
                        fputs(ring[j], stdout);
                        free(ring[j]);
                }
+               if (r) {
+                       writerune("<stdout>", stdout, &r[j]);
+               }
        } while ((j = (j + 1) % n) != i);
 
        free(ring);
@@ -63,30 +81,32 @@ main(int argc, char *argv[])
 {
        struct stat st1, st2;
        FILE *fp;
-       size_t n = 10, tmpsize;
+       size_t num = 10, tmpsize;
        int ret = 0, newline, many;
-       char *lines, *tmp;
-       void (*tail)(FILE *, const char *, size_t) = taketail;
+       char mode = 'n', *numstr, *tmp;
+       void (*tail)(FILE *, const char *, size_t, char) = taketail;
 
        ARGBEGIN {
        case 'f':
                fflag = 1;
                break;
+       case 'c':
        case 'n':
-               lines = EARGF(usage());
-               n = MIN(llabs(estrtonum(lines, LLONG_MIN + 1, MIN(LLONG_MAX, 
SIZE_MAX))), SIZE_MAX);
-               if (strchr(lines, '+'))
+               mode = ARGC();
+               numstr = EARGF(usage());
+               num = MIN(llabs(estrtonum(numstr, LLONG_MIN + 1, MIN(LLONG_MAX, 
SIZE_MAX))), SIZE_MAX);
+               if (strchr(numstr, '+'))
                        tail = dropinit;
                break;
        ARGNUM:
-               n = ARGNUMF();
+               num = ARGNUMF();
                break;
        default:
                usage();
        } ARGEND;
 
        if (argc == 0)
-               tail(stdin, "<stdin>", n);
+               tail(stdin, "<stdin>", num, mode);
        else {
                if ((many = argc > 1) && fflag)
                        usage();
@@ -104,7 +124,7 @@ main(int argc, char *argv[])
                        if (!(S_ISFIFO(st1.st_mode) || S_ISREG(st1.st_mode)))
                                fflag = 0;
                        newline = 1;
-                       tail(fp, argv[0], n);
+                       tail(fp, argv[0], num, mode);
 
                        if (fflag && argc == 1) {
                                tmp = NULL;

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