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/* ISC license. */
#include <sys/types.h>
#include <sys/uio.h>
#include <errno.h>
#include <skalibs/sgetopt.h>
#include <skalibs/allreadwrite.h>
#include <skalibs/types.h>
#include <skalibs/buffer.h>
#include <skalibs/strerr.h>
#include <skalibs/djbunix.h>
#include <skalibs/skamisc.h>
#include <skalibs/siovec.h>
#define USAGE "s6-tail [ -c chars | -n lines | -1..9 ] [ file ]"
typedef int tail_func (int, size_t) ;
typedef tail_func *tail_func_ref ;
static int tail_pluslines (int fd, size_t n)
{
if (n) n-- ;
{
char buf[BUFFER_INSIZE] ;
buffer b = BUFFER_INIT(&buffer_read, fd, buf, BUFFER_INSIZE) ;
size_t count = 0 ;
while (count < n)
{
ssize_t r = buffer_fill(&b) ;
if (r <= 0) return !r ;
while (!buffer_isempty(&b) && (count < n))
{
struct iovec v[2] ;
size_t i ;
buffer_rpeek(&b, v) ;
i = siovec_bytechr(v, 2, '\n') ;
if (i < buffer_len(&b))
{
count++ ; i++ ;
}
buffer_rseek(&b, i) ;
}
}
b.op = &buffer_write ;
b.fd = 1 ;
if (!buffer_flush(&b)) return 0 ;
}
return (fd_cat(fd, 1) >= 0) ;
}
static int tail_pluschars (int fd, size_t n)
{
if (n-- > 1)
{
int nil = open_write("/dev/null") ;
if (nil < 0) return 0 ;
if (!fd_catn(fd, nil, n))
{
fd_close(nil) ;
return 0 ;
}
fd_close(nil) ;
}
return (fd_cat(fd, 1) >= 0) ;
}
static int tail_minuslines (int fd, size_t n)
{
char buf[BUFFER_INSIZE] ;
buffer b = BUFFER_INIT(&buffer_read, fd, buf, BUFFER_INSIZE) ;
size_t head = 0, tail = 0 ;
stralloc tab[n+1] ;
for (; head <= n ; head++) tab[head] = stralloc_zero ;
head = 0 ;
for (;;)
{
int r ;
r = skagetln(&b, tab + tail, '\n') ;
if (!r) break ;
if (r < 0)
{
if (errno == EPIPE) break ;
else goto err ;
}
tail = (tail + 1) % (n+1) ;
if (tail == head)
{
tab[head].len = 0 ;
head = (head + 1) % (n+1) ;
}
}
buffer_init(&b, &buffer_write, 1, buf, BUFFER_INSIZE) ;
for (; head != tail ; head = (head + 1) % (n+1))
{
if (buffer_put(&b, tab[head].s, tab[head].len) < tab[head].len)
goto err ;
}
for (head = 0 ; head <= n ; head++) stralloc_free(tab + head) ;
return buffer_flush(&b) ;
err:
for (head = 0 ; head <= n ; head++) stralloc_free(tab + head) ;
return 0 ;
}
static int tail_minuschars (int fd, size_t n)
{
char buf[BUFFER_INSIZE + n] ;
buffer b = BUFFER_INIT(&buffer_read, fd, buf, BUFFER_INSIZE + n) ;
for (;;)
{
ssize_t r = buffer_fill(&b) ;
if (!r) break ;
if (r < 0) return 0 ;
buffer_rseek(&b, buffer_len(&b)) ;
buffer_unget(&b, n) ;
}
b.op = &buffer_write ;
b.fd = 1 ;
return buffer_flush(&b) ;
}
int main (int argc, char const *const *argv)
{
tail_func_ref f = &tail_minuslines ;
unsigned int n = 10 ;
int gotit = 0 ;
PROG = "s6-tail" ;
{
subgetopt l = SUBGETOPT_ZERO ;
for (;;)
{
int opt = subgetopt_r(argc, argv, "123456789n:c:", &l) ;
if (opt == -1) break ;
switch (opt)
{
case '1' :
case '2' :
case '3' :
case '4' :
case '5' :
case '6' :
case '7' :
case '8' :
case '9' :
{
if (gotit) strerr_dieusage(100, USAGE) ;
gotit = 1 ;
f = &tail_minuslines ;
n = opt - '0' ;
break ;
}
case 'n':
{
if (gotit) strerr_dieusage(100, USAGE) ;
gotit = 1 ;
f = &tail_minuslines ;
if (*l.arg == '-') l.arg++ ;
else if (*l.arg == '+')
{
f = &tail_pluslines ;
l.arg++ ;
}
if (!uint0_scan(l.arg, &n)) strerr_dieusage(100, USAGE) ;
break ;
}
case 'c':
{
if (gotit) strerr_dieusage(100, USAGE) ;
gotit = 1 ;
f = &tail_minuschars ;
if (*l.arg == '-') l.arg++ ;
else if (*l.arg == '+')
{
f = &tail_pluschars ;
l.arg++ ;
}
if (!uint0_scan(l.arg, &n)) strerr_dieusage(100, USAGE) ;
break ;
}
default : strerr_dieusage(100, USAGE) ;
}
}
argc -= l.ind ; argv += l.ind ;
}
if (!argc)
{
if (!(*f)(0, n))
strerr_diefu1sys(111, "tail stdin") ;
}
else
{
int fd = open_readb(argv[0]) ;
if (fd == -1) strerr_diefu3sys(111, "open ", argv[0], " for reading") ;
if (!(*f)(fd, n))
strerr_diefu2sys(111, "tail ", argv[0]) ;
fd_close(fd) ;
}
return 0 ;
}
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