logwrapper.c revision 4f6e8d7a00cbeda1e70cc15be9c4af1018bdad53 
1/*
2 * Copyright (C) 2008 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#include <string.h>
18#include <sys/types.h>
19#include <sys/wait.h>
20#include <stdio.h>
21#include <stdlib.h>
22#include <unistd.h>
23#include <errno.h>
24
25#include "cutils/log.h"
26
27void fatal(const char *msg) {
28    fprintf(stderr, msg);
29    LOG(LOG_ERROR, "logwrapper", msg);
30    exit(-1);
31}
32
33void usage() {
34    fatal(
35        "Usage: logwrapper BINARY [ARGS ...]\n"
36        "\n"
37        "Forks and executes BINARY ARGS, redirecting stdout and stderr to\n"
38        "the Android logging system. Tag is set to BINARY, priority is\n"
39        "always LOG_INFO.\n");
40}
41
42void parent(const char *tag, int parent_read) {
43    int status;
44    char buffer[1024];
45
46    int a = 0;  // start index of unprocessed data
47    int b = 0;  // end index of unprocessed data
48    int sz;
49    while ((sz = read(parent_read, &buffer[b], 1023 - b)) > 0) {
50        // Log one line at a time
51        for (b = a; b < sz; b++) {
52            if (buffer[b] == '\n') {
53                buffer[b] = '\0';
54                LOG(LOG_INFO, tag, &buffer[a]);
55                a = b + 1;
56            }
57        }
58
59        if (a == 0 && b == 1023) {
60            // buffer is full, flush
61            buffer[b] = '\0';
62            LOG(LOG_INFO, tag, &buffer[a]);
63            b = 0;
64        } else {
65            // Keep left-overs
66            b = sz - a;
67            memmove(buffer, &buffer[a], b);
68            a = 0;
69        }
70    }
71    // Flush remaining data
72    if (a != b) {
73        buffer[b] = '\0';
74        LOG(LOG_INFO, tag, &buffer[a]);
75    }
76    wait(&status);  // Wait for child
77}
78
79void child(int argc, char* argv[]) {
80    // create null terminated argv_child array
81    char* argv_child[argc + 1];
82    memcpy(argv_child, argv, argc * sizeof(char *));
83    argv_child[argc] = NULL;
84
85    if (execvp(argv_child[0], argv_child)) {
86        LOG(LOG_ERROR, "logwrapper",
87            "executing %s failed: %s\n", argv_child[0], strerror(errno));
88        exit(-1);
89    }
90}
91
92int main(int argc, char* argv[]) {
93    pid_t pid;
94
95    int pipe_fds[2];
96    int *parent_read = &pipe_fds[0];
97    int *child_write = &pipe_fds[1];
98
99    if (argc < 2) {
100        usage();
101    }
102
103    if (pipe(pipe_fds) < 0) {
104        fatal("Cannot create pipe\n");
105    }
106
107    pid = fork();
108    if (pid < 0) {
109        fatal("Failed to fork\n");
110    } else if (pid == 0) {
111        // redirect stdout and stderr
112        close(*parent_read);
113        dup2(*child_write, 1);
114        dup2(*child_write, 2);
115        close(*child_write);
116
117        child(argc - 1, &argv[1]);
118
119    } else {
120        close(*child_write);
121
122        parent(argv[1], *parent_read);
123    }
124
125    return 0;
126}
127