写入简单的日志log

log.c：

#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <time.h>
#include <unistd.h>

#include "log.h"

void logmessage(char *logheader, char *fmt, ...)
{
    va_list args;
    char buf[];

    va_start(args, fmt);
    vsnprintf(buf, sizeof(buf) - , fmt, args);

    openlog(logheader, , );

    syslog(, buf);

    closelog();
    va_end(args);

    return;
}

void logcurrent(const char *func, int line, char *fmt, ...)
{
    va_list args;
    FILE *fp = NULL;
    char tmp[];
    char buf[];
    char log_message[];
    char *path;
    char *time_s;
    time_t t;

    time_s = tmp;

    t = time(NULL);
    time_s = ctime(&t);
    time_s[strlen(time_s) - ] = ' '; // remove '\n'

    va_start(args, fmt);
    vsnprintf(log_message, sizeof(log_message) - , fmt, args);
    printf("log_message : %s\n", log_message);

    snprintf(buf, sizeof(buf) - , "%s %s[%d] %s", time_s, func, line, log_message);
    printf("buf : %s\n", buf);

    path = get_current_dir_name();

    strcat(path, "/log.text");

    fp = fopen(path, "a+");
    if (fp == NULL) {
        perror("fopen");
        return;
    }

    if (fwrite(buf, strlen(buf), , fp) == ) {
        perror("fwrite");
        return;
    }

    if (fp) {
        fclose(fp);
    }

    va_end(args);

    return;
}

int main(void)
{
    tcp_log("%s", "1234567890z");
    logcurrent(__func__, __LINE__, "abc\n");
}

log.h：

#ifndef __LOG_H__
#define __LOG_H__

#ifndef SYS_LOG
#define tcp_log(fmt, args...) logcurrent(__func__, __LINE__, fmt, ## args)
#else
#define tcp_log(fmt, args...) logmessage(log_header, fmt, ## args)
#endif
#endif

Makefile:

CC = gcc
TARGET = log-test
SOURCE = log.c

all: clean
    $(CC) $(SOURCE) -o $(TARGET)

clean:
    rm -rf $(TARGET)