A larger buffer won't help. Setting the buffer size to zero won't help. The problem is that each vfprintf() call can generate multiple calls to write() - the calls that actually write the data to the file. Each individual write() call is guaranteed to be atomic, but a series of multiple write() calls from different processes and/or threads will wind up as you're seeing - all interleaved together.
You need to make certain each call to your writeLog() function results in one and only one underlying write() call.
write(). Not fwrite() or fprintf().
In theory, you could pass a zero length to the first call to vsnprintf() and get back the known length of the final string. In practice there are still vsnprintf() implementations that don't do that per current standards. (The old SUSv2 standard specified different return values.)
I need to create a shared library to access an in memory DB. The DB is not huge, but big enough to make it cumbersome to carry around in every single process using the shared library. Luckily, it is pretty static information, so I don't need to worry much about synchronizing the data between... (12 Replies)
Hi all,
Well I've had a bit more experience with Unix-like environments since my last post, now that I have started working on my website in earnest and am doing much of the file manipulation via the command line through SSH.
The thing is, I want to be able to log all console activity,... (4 Replies)
I am writing a shared library in Linux (but compatible with other UNIXes) and I want to allow multiple instances to share a piece of memory -- 1 byte is enough. What's the "best" way to do this? I want to optimize for speed and portability.
Obviously, I'll have to worry about mutual exclusion. (0 Replies)
I am trying to figure a way to have a log file and still keep the output in the terminal in a script.
The example below logs to a file nicely but i still want the output in the terminal as well
#!/bin/bash
#Create a log
exec >> /path/to/my/logfile
echo "hello world"
Any help would be... (3 Replies)
We are trying to install third party software on this unix server...
Here is the error message we are getting...
error while loading shared libraries: libodbc.so.1: cannot open shared object file: No such file or directory
It seems like odbc driver is not installed...
>rpm -q unixODBC... (1 Reply)
Hello.
I am new to this forum and I would like to ask for advice about low level POSIX programming.
I have to implement a POSIX compliant C shared library.
A file will have some variables and the shared library will have some functions which need those variables.
There is one special... (5 Replies)
Hi,
I've the following code to log the errors any after the command is executed.
# Ksh 88 Version
log_path=/home/etc/fls/fls_log.log
del_path=/home/etc/fls/to_day
rm $del_path/* >> $log_path 2>&1
But I even want to log if the rm command is success without any error along with... (1 Reply)
When unlocking a Linux server's console there's no event indicating successful logging
Is there a way I can fix this ?
I have the following in my rsyslog.conf
auth.info /var/log/secure
authpriv.info /var/log/secure (1 Reply)
Hi,
While running tcpdump command on my Fedora 16 machine I am get shared library issue.
# tcpdump
tcpdump: error while loading shared libraries: libcrypto.so.6: cannot open shared object file: No such file or directory
# which tcpdump
/usr/software/sbin/tcpdump
I have tried... (3 Replies)
Discussion started by: muzaffar.k
3 Replies
LEARN ABOUT OSF1
vprintf
vprintf(3) Library Functions Manual vprintf(3)NAME
vprintf, vfprintf, vsnprintf, vsprintf - Format a variable number of parameters for output
LIBRARY
Standard C Library (libc.so, libc.a)
SYNOPSIS
#include <stdarg.h> #include <stdio.h>
int vprintf(
const char *format,
va_list printarg);
int vfprintf(
FILE *stream,
const char *format,
va_list printarg);
int vsnprintf(
char *string, size_t n,
const char *format,
va_list printarg);
int vsprintf(
char *string,
const char *format,
va_list printarg);
STANDARDS
Interfaces documented on this reference page conform to industry standards as follows:
vfprintf(), vprintf(), vsnprintf(), vsprintf(): ISO C, XPG4, XPG4-UNIX
Refer to the standards(5) reference page for more information about industry standards and associated tags.
PARAMETERS
Specifies a character string that contains two types of objects: Plain characters, which are copied to the output stream. Conversion spec-
ifications, each of which causes zero or more items to be fetched from the stdarg parameter lists. Specifies the arguments to be printed.
Specifies the output stream. Specifies the buffer to which output is printed. Specifies the size of the buffer referred to by string.
DESCRIPTION
The vprintf(), vfprintf(), vsnprintf(), and vsprintf() functions format and write stdarg parameter lists.
These functions are the same as the printf(), fprintf(), snprintf(), and sprintf() functions, respectively, except that these functions are
not called with a variable number of parameters. Instead, vprintf(), vfprintf(), vsnprintf(), and vsprintf() are called with a parameter
list pointer as defined by stdarg. Because these functions invoke the va_arg() macro and not the va_end() macro, the value of printarg is
indeterminate after a return. Therefore, applications should execute a call to the va_end() macro after a call to one of these functions.
EXAMPLES
The following example demonstrates how the vfprintf() function can be used to write an error routine:
#include <stdarg.h> #include <stdio.h>
void error(char *funct, char *fmt, ...) {
va_list args;
/*
** Display the name of the function that called error
*/
fprintf(stderr, "ERROR in %s: ", funct);
/*
** Display the remainder of the message
*/
va_start(args, fmt);
vfprintf(stderr, fmt, args);
va_end(args);
abort(); }
RELATED INFORMATION
Functions: fopen(3), printf(3), vwprintf(3), wprintf(3) delim off
vprintf(3)