1/* truncate.c - set file length, extending sparsely if necessary
2 *
3 * Copyright 2011 Rob Landley <rob@landley.net>
4
5USE_TRUNCATE(NEWTOY(truncate, "<1s:|c", TOYFLAG_BIN))
6
7config TRUNCATE
8  bool "truncate"
9  default y
10  help
11    usage: truncate [-c] -s SIZE file...
12
13    Set length of file(s), extending sparsely if necessary.
14
15    -c	Don't create file if it doesn't exist
16    -s	New size (with optional prefix and suffix)
17
18    SIZE prefix: + add, - subtract, < shrink to, > expand to,
19                 / multiple rounding down, % multiple rounding up
20    SIZE suffix: k=1024, m=1024^2, g=1024^3, t=1024^4, p=1024^5, e=1024^6
21*/
22
23#define FOR_truncate
24#include "toys.h"
25
26GLOBALS(
27  char *s;
28
29  long size;
30  int type;
31)
32
33static void do_truncate(int fd, char *name)
34{
35  long long size;
36
37  if (fd<0) return;
38
39  if (TT.type == -1) size = TT.size;
40  else {
41    size = fdlength(fd);
42    if (TT.type<2) size += TT.size*(1-(2*TT.type));
43    else if (TT.type<4) {
44      if ((TT.type==2) ? (size <= TT.size) : (size >= TT.size)) return;
45      size = TT.size;
46    } else {
47      size = (size+(TT.type-4)*(TT.size-1))/TT.size;
48      size *= TT.size;
49    }
50  }
51  if (ftruncate(fd, size)) perror_msg("'%s' to '%lld'", name, size);
52}
53
54void truncate_main(void)
55{
56  int cr = !(toys.optflags&FLAG_c);
57
58  if (-1 != (TT.type = stridx("+-<>/%", *TT.s))) TT.s++;
59  TT.size = atolx(TT.s);
60
61  // Create files with mask rwrwrw.
62  // Nonexistent files are only an error if we're supposed to create them.
63  loopfiles_rw(toys.optargs, O_WRONLY|O_CLOEXEC|(cr ? O_CREAT|WARN_ONLY : 0),
64    0666, do_truncate);
65}
66