1 /*
2 * Copyright (c) 2013 Apple Inc. All rights reserved.
3 *
4 * @APPLE_LICENSE_HEADER_START@
5 *
6 * This file contains Original Code and/or Modifications of Original Code
7 * as defined in and that are subject to the Apple Public Source License
8 * Version 2.0 (the 'License'). You may not use this file except in
9 * compliance with the License. Please obtain a copy of the License at
10 * http://www.opensource.apple.com/apsl/ and read it before using this
11 * file.
12 *
13 * The Original Code and all software distributed under the License are
14 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
15 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
16 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
18 * Please see the License for the specific language governing rights and
19 * limitations under the License.
20 *
21 * @APPLE_LICENSE_HEADER_END@
22 */
23
24 #include <stdio.h>
25 #include <stdlib.h>
26 #include <unistd.h>
27 #include <string.h>
28 #include <stdbool.h>
29 #include <errno.h>
30 #include <err.h>
31 #include <sysexits.h>
32
33 #include <sys/stat.h>
34 #include <sys/fcntl.h>
35 #include <sys/param.h>
36 #include <sys/time.h>
37
38 void usage(void);
39
40 int
main(int argc,char * argv[])41 main(int argc, char * argv[])
42 {
43 struct stat sb;
44 char *newcontent = NULL;
45 size_t newcontentlength = 0;
46 char *oldcontent = NULL;
47 int ret;
48 int dstfd;
49 const char *dst = NULL;
50 ssize_t readsize, writesize;
51 int i;
52
53 if (argc < 2) {
54 usage();
55 }
56
57 dst = argv[1];
58
59 for (i = 2; i < argc; i++) {
60 newcontentlength += strlen(argv[i]) + 1 /* space or newline */;
61 }
62 newcontentlength += 1; /* NUL */
63
64 newcontent = malloc(newcontentlength);
65 if (newcontent == NULL) {
66 err(EX_UNAVAILABLE, "malloc() failed");
67 }
68
69 newcontent[0] = '\0';
70
71 for (i = 2; i < argc; i++) {
72 strlcat(newcontent, argv[i], newcontentlength);
73 if (i < argc - 1) {
74 strlcat(newcontent, " ", newcontentlength);
75 } else {
76 strlcat(newcontent, "\n", newcontentlength);
77 }
78 }
79
80 dstfd = open(dst, O_RDWR | O_CREAT | O_APPEND, DEFFILEMODE);
81 if (dstfd < 0) {
82 err(EX_NOINPUT, "open(%s)", dst);
83 }
84
85 ret = fstat(dstfd, &sb);
86 if (ret < 0) {
87 err(EX_NOINPUT, "fstat(%s)", dst);
88 }
89
90 if (!S_ISREG(sb.st_mode)) {
91 err(EX_USAGE, "%s is not a regular file", dst);
92 }
93
94 if (sb.st_size != newcontentlength) {
95 /* obvious new content must be different than old */
96 goto replace;
97 }
98
99 oldcontent = malloc(newcontentlength);
100 if (oldcontent == NULL) {
101 err(EX_UNAVAILABLE, "malloc(%lu) failed", newcontentlength);
102 }
103
104 readsize = read(dstfd, oldcontent, newcontentlength);
105 if (readsize == -1) {
106 err(EX_UNAVAILABLE, "read() failed");
107 } else if (readsize != newcontentlength) {
108 errx(EX_UNAVAILABLE, "short read of file");
109 }
110
111 if (0 == memcmp(oldcontent, newcontent, newcontentlength)) {
112 /* binary comparison succeeded, just exit */
113 free(oldcontent);
114 ret = close(dstfd);
115 if (ret < 0) {
116 err(EX_UNAVAILABLE, "close() failed");
117 }
118
119 exit(0);
120 }
121
122 replace:
123 ret = ftruncate(dstfd, 0);
124 if (ret < 0) {
125 err(EX_UNAVAILABLE, "ftruncate() failed");
126 }
127
128 writesize = write(dstfd, newcontent, newcontentlength);
129 if (writesize == -1) {
130 err(EX_UNAVAILABLE, "write() failed");
131 } else if (writesize != newcontentlength) {
132 errx(EX_UNAVAILABLE, "short write of file");
133 }
134
135 ret = close(dstfd);
136 if (ret < 0) {
137 err(EX_NOINPUT, "close(dst)");
138 }
139
140 return 0;
141 }
142
143 void
usage(void)144 usage(void)
145 {
146 fprintf(stderr, "Usage: %s <dst> <new> <contents> <...>\n",
147 getprogname());
148 exit(EX_USAGE);
149 }
150