Add implementation of dd(1)
This commit is contained in:
Michael Forney
parent
92f17ad648
commit
6ff6bb57ce
1
.gitignore
vendored
1
.gitignore
vendored
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@ -17,6 +17,7 @@
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/cron
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/cut
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/date
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/dd
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/dirname
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/du
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/echo
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91
dd.1
Normal file
91
dd.1
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.Dd 2020-04-28
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.Dt DD 1
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.Os sbase
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.Sh NAME
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.Nm dd
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.Nd convert and copy a file
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.Sh SYNOPSIS
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.Nm
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.Op Ar operand Ns ...
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.Sh DESCRIPTION
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.Nm
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copies its input to its output, possibly after conversion, using
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the specified block sizes,
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.Pp
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The following operands are available:
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.Bl -tag -width ibs=expr
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.It Cm if= Ns Ar file
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Read from the file named by
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.Ar file
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instead of standard input.
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.It Cm of= Ns Ar file
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Write to the file named by
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.Ar file
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instead of standard output.
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.It Cm ibs= Ns Ar expr
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Set the input block size to
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.Ar expr
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(defaults to 512).
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.It Cm obs= Ns Ar expr
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Set the output block size to
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.Ar expr
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(defaults to 512).
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.It Cm bs= Ns Ar expr
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Set the input and output block sizes to
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.Ar expr .
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Additionally, if no conversion other than
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.Cm noerror ,
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.Cm notrunc ,
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or
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.Cm sync
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is specified, input blocks are copied as single output blocks, even
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when the input block is short.
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.It Cm skip= Ns Ar n
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Skip
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.Ar n
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input blocks before starting to copy.
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.It Cm seek= Ns Ar n
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Skip
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.Ar n
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output blocks before starting to copy.
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.It Cm count= Ns Ar n
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Copy at most
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.Ar n
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input blocks.
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.It Cm conv= Ns Ar value Ns Op , Ns Ar value Ns ...
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Apply the conversions specified by
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.Ar value .
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.Bl -tag -width Ds
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.It Cm lcase
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Map uppercase characters to the corresponding lowercase character
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using
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.Fn tolower .
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.It Cm ucase
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Map lowercase characters to the corresponding uppercase character
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using
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.Fn toupper .
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.It Cm swab
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Swap each pair of bytes in the input block.
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If there is an odd number of bytes in a block, the last one is
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unmodified.
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.It Cm noerror
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In case of an error reading from the input, do not fail.
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Instead, print a diagnostic message and a summary of the current
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status.
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.It Cm notrunc
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Do not truncate the output file.
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.It Cm sync
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In case of a partial input block, pad with null bytes to form a
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complete block.
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.El
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.El
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.Sh STANDARDS
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The
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.Nm
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utility is compliant with the
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.St -p1003.1-2008
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specification, except that it does not implement the
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.Cm block
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and
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.Cm unblock
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conversions.
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234
dd.c
Normal file
234
dd.c
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@ -0,0 +1,234 @@
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/* See LICENSE file for copyright and license details. */
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#include <ctype.h>
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#include <fcntl.h>
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#include <inttypes.h>
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#include <stdint.h>
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#include <string.h>
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#include <unistd.h>
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#include "util.h"
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static off_t ifull, ofull, ipart, opart;
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static void
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usage(void)
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{
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eprintf("usage: %s [operand...]\n", argv0);
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}
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static size_t
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parsesize(char *expr)
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{
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char *s = expr;
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size_t n = 1;
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for (;;) {
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n *= strtoumax(s, &s, 10);
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switch (*s) {
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case 'k': n <<= 10; s++; break;
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case 'b': n <<= 9; s++; break;
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}
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if (*s != 'x' || !s[1])
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break;
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s++;
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}
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if (*s || n == 0)
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eprintf("invalid block size expression '%s'\n", expr);
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return n;
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}
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static void
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bswap(unsigned char *buf, size_t len)
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{
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int c;
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for (len &= ~1; len > 0; buf += 2, len -= 2) {
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c = buf[0];
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buf[0] = buf[1];
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buf[1] = c;
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}
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}
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static void
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lcase(unsigned char *buf, size_t len)
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{
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for (; len > 0; buf++, len--)
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buf[0] = tolower(buf[0]);
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}
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static void
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ucase(unsigned char *buf, size_t len)
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{
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for (; len > 0; buf++, len--)
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buf[0] = toupper(buf[0]);
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}
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static void
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summary(void)
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{
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fprintf(stderr, "%"PRIdMAX"+%"PRIdMAX" records in\n", (intmax_t)ifull, (intmax_t)ipart);
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fprintf(stderr, "%"PRIdMAX"+%"PRIdMAX" records out\n", (intmax_t)ofull, (intmax_t)opart);
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}
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int
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main(int argc, char *argv[])
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{
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enum {
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LCASE = 1 << 0,
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UCASE = 1 << 1,
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SWAB = 1 << 2,
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NOERROR = 1 << 3,
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NOTRUNC = 1 << 4,
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SYNC = 1 << 5,
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} conv = 0;
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char *arg, *val, *end;
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const char *iname = "-", *oname = "-";
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int ifd = 0, ofd = 1, eof = 0;
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size_t len, bs = 0, ibs = 512, obs = 512, ipos = 0, opos = 0;
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off_t skip = 0, seek = 0, count = -1;
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ssize_t ret;
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unsigned char *buf;
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argv0 = argc ? (argc--, *argv++) : "dd";
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for (; argc > 0; argc--, argv++) {
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arg = *argv;
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val = strchr(arg, '=');
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if (!val)
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usage();
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*val++ = '\0';
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if (strcmp(arg, "if") == 0) {
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iname = val;
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} else if (strcmp(arg, "of") == 0) {
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oname = val;
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} else if (strcmp(arg, "ibs") == 0) {
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ibs = parsesize(val);
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} else if (strcmp(arg, "obs") == 0) {
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obs = parsesize(val);
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} else if (strcmp(arg, "bs") == 0) {
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bs = parsesize(val);
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} else if (strcmp(arg, "skip") == 0) {
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skip = estrtonum(val, 0, LLONG_MAX);
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} else if (strcmp(arg, "seek") == 0) {
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seek = estrtonum(val, 0, LLONG_MAX);
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} else if (strcmp(arg, "count") == 0) {
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count = estrtonum(val, 0, LLONG_MAX);
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} else if (strcmp(arg, "conv") == 0) {
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do {
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end = strchr(val, ',');
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if (end)
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*end++ = '\0';
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if (strcmp(val, "lcase") == 0)
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conv |= LCASE;
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else if (strcmp(val, "ucase") == 0)
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conv |= UCASE;
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else if (strcmp(val, "swab") == 0)
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conv |= SWAB;
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else if (strcmp(val, "noerror") == 0)
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conv |= NOERROR;
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else if (strcmp(val, "notrunc") == 0)
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conv |= NOTRUNC;
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else if (strcmp(val, "sync") == 0)
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conv |= SYNC;
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else
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eprintf("unknown conv flag '%s'\n", val);
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val = end;
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} while (val);
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} else {
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weprintf("unknown operand '%s'\n", arg);
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usage();
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}
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}
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if (bs)
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ibs = obs = bs;
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if (strcmp(iname, "-") != 0) {
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ifd = open(iname, O_RDONLY);
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if (ifd < 0)
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eprintf("open %s:", iname);
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}
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if (strcmp(oname, "-") != 0) {
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ofd = open(oname, O_WRONLY | O_CREAT | (conv & NOTRUNC || seek ? 0 : O_TRUNC), 0666);
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if (ofd < 0)
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eprintf("open %s:", oname);
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}
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len = MAX(ibs, obs) + ibs;
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buf = emalloc(len);
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if (skip && lseek(ifd, skip * ibs, SEEK_SET) < 0) {
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while (skip--) {
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ret = read(ifd, buf, ibs);
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if (ret < 0)
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eprintf("read:");
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if (ret == 0) {
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eof = 1;
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break;
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}
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}
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}
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if (seek) {
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if (!(conv & NOTRUNC) && ftruncate(ofd, seek * ibs) != 0)
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eprintf("ftruncate:");
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if (lseek(ofd, seek * ibs, SEEK_SET) < 0)
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eprintf("lseek:");
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/* XXX: handle non-seekable files */
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}
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while (!eof && (count == -1 || ifull + ipart < count)) {
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while (ipos - opos < obs) {
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ret = read(ifd, buf + ipos, ibs);
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if (ret == 0) {
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eof = 1;
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break;
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}
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if (ret < 0) {
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weprintf("read:");
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if (!(conv & NOERROR))
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return 1;
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summary();
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if (!(conv & SYNC))
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continue;
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ret = 0;
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}
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if (ret < ibs) {
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ipart++;
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if (conv & SYNC) {
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memset(buf + ipos + ret, 0, ibs - ret);
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ret = ibs;
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}
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} else {
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ifull++;
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}
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if (conv & SWAB)
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bswap(buf + ipos, ret);
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if (conv & LCASE)
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lcase(buf + ipos, ret);
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if (conv & UCASE)
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ucase(buf + ipos, ret);
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ipos += ret;
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if (bs && !(conv & (SWAB | LCASE | UCASE)))
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break;
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}
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if (ipos == opos)
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break;
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do {
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ret = write(ofd, buf + opos, MIN(obs, ipos - opos));
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if (ret < 0)
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eprintf("write:");
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if (ret == 0)
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eprintf("write returned 0\n");
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if (ret < obs)
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opart++;
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else
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ofull++;
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opos += ret;
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} while ((eof && ipos < opos) || (!eof && ipos - opos >= obs));
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if (len - ipos < ibs) {
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memmove(buf, buf + opos, ipos - opos);
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ipos -= opos;
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opos = 0;
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}
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}
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summary();
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return 0;
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}
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