1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
|
/*
* mispipe: written by Nathanael Nerode.
*
* Copyright 2004 Nathanael Nerode.
*
* Licensed under the GPL version 2 or above, and dual-licensed under the
* following license:
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
/*
* Usage: mispipe <command1> <command2>
* Run <command1> | <command2>, but return with the exit status of <command1>.
*
* This is designed for a very specific purpose: logging.
* "foo | logger -t foo"
* will return with the exit status of logger, not that of foo.
* "mispipe foo 'logger -t foo'"
* will return with the exit status of foo.
*/
/*
* To do:
* Make this into a fancy, internationalized, option-handling hellbeast.
* (But why bother? It does its job quite well.)
*/
#include <errno.h> /* errno */
#include <sys/types.h>
#include <unistd.h> /* pipe(), fork(),... */
#include <stdlib.h> /* system() */
#include <sys/wait.h> /* waitpid(), etc. */
#include <stdio.h>
#include <stdarg.h> /* va_list, for error() */
static const char* progname; /* Stores argv[0] */
static int filedes[2]; /* Stores pipe file descriptors */
/* Subroutine for 'warning' and 'error' which prefixes progname */
static void warning_prefix(void) {
fputs(progname, stderr);
fputs(": ", stderr);
}
/* Issue a warning, then die */
__attribute__(( noreturn, format (printf, 1, 2) ))
static void error(const char* formatstr, ...) {
va_list ap;
va_start(ap, formatstr);
warning_prefix();
vfprintf(stderr, formatstr, ap);
va_end(ap);
exit(1);
}
/* Issue a warning, then die, with errno */
__attribute__(( noreturn ))
static void error_with_errno(const char* message) {
int saved_errno;
saved_errno=errno;
warning_prefix();
fputs(message, stderr);
fputs(": error number ", stderr);
fprintf(stderr, "%i\n", saved_errno);
exit(1);
}
/* Convert 'wait'/'system'-style exit status to 'exit'-style exit status */
__attribute__(( const ))
static int shorten_status(int status_big) {
if (WIFEXITED(status_big))
return WEXITSTATUS(status_big);
if (WIFSIGNALED(status_big))
return 128+WTERMSIG(status_big);
if (WIFSTOPPED(status_big))
return 128+WSTOPSIG(status_big);
#ifdef WCOREDUMP
if (WCOREDUMP(status_big))
error("Ow, somebody dumped core!");
#endif
error("shorten_status got an invalid status (?!)");
}
/* All the work for command 2. */
__attribute__(( noreturn ))
static void subprocess2(const char* cmd) {
/* Close the old standard input. */
if (close(0))
error_with_errno("Failed (in child) closing standard input");
/* Make the reading end of the pipe the new standard input. */
if (dup2(filedes[0], 0) == -1)
error_with_errno("Failed (in child) redefining standard input");
/* Close the other end of the pipe. */
if (close(filedes[1]))
error_with_errno("Failed (in child) closing filedes[1]");
/* Do the second command, and throw away the exit status. */
system(cmd);
/* Close all the file descriptors. */
if (close(filedes[0]))
error_with_errno("Failed (in child) closing filedes[0]"
" (while cleaning up)");
if (close(0))
error_with_errno("Failed (in child) closing standard output "
" (while cleaning up)");
exit(0);
}
int main (int argc, const char ** argv) {
int status_big; /* Exit status, 'wait' and 'system' style */
pid_t child2_pid;
pid_t dead_pid;
/* Set progname */
progname = argv[0];
/* Verify arguments */
if (argc != 3)
error("Wrong number of args, aborting\n");
/* Open a new pipe */
if (pipe(filedes))
error_with_errno("pipe() failed");
/* Fork to run second command */
child2_pid = fork();
if (child2_pid == 0)
subprocess2(argv[2]);
if (child2_pid == -1)
error_with_errno("fork() failed");
/* Run first command inline (seriously!) */
/* Close standard output. */
if (close(1))
error_with_errno("Failed closing standard output");
/* Make the writing end of the pipe the new standard output. */
if (dup2(filedes[1], 1) == -1)
error_with_errno("Failed redefining standard output");
/* Close the other end of the pipe. */
if (close(filedes[0]))
error_with_errno("Failed closing filedes[0]");
/* Do the first command, and (crucially) get the status. */
status_big = system(argv[1]);
/* Close the pipe "standard output". */
if (close(filedes[1]))
error_with_errno("Failed closing filedes[1] (while cleaning up)");
/* Close standard output. */
if (close(1))
error_with_errno("Failed closing standard output (while cleaning up)");
/* Wait for the other process to exit. */
/* We don't care about the status. */
dead_pid = waitpid(child2_pid, NULL, WUNTRACED);
if (dead_pid == -1) {
error_with_errno("waitpid() failed");
}
else if (dead_pid != child2_pid) {
error("waitpid(): Who died? %i\n", dead_pid);
}
/* Return the desired exit status. */
return shorten_status(status_big);
}
|
