1 /* truncate.c - set file length, extending sparsely if necessary
2 *
3 * Copyright 2011 Rob Landley <rob@landley.net>
4
5 USE_TRUNCATE(NEWTOY(truncate, "<1s:|c", TOYFLAG_BIN))
6
7 config 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
GLOBALS(char * s;long size;int type;)26 GLOBALS(
27 char *s;
28
29 long size;
30 int type;
31 )
32
33 static 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
truncate_main(void)54 void truncate_main(void)
55 {
56 int cr = !(toys.optflags&1);
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 : 0), 0666, cr,
64 do_truncate);
65 }
66