split command

01-12-2010

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IMO, you are missing the point. sync(), fdatasync(), fsync() force the kernel to write to disk/device all pending write operations - fsync() works on a single stream...fflush() calls fsync(). If a process abends without flushing stdout the output is lost period.

If your process IS ACTUALLY writing everything before it dies, then the problem lies with split. Which I doubt. Can you post the last few lines of output from your app (do not use split) when it hits error conditions?

For example: If you call _exit() rather than exit() in your code it will NOT flush output.

example 1:

Code:

#include <signal.h>                
#include <stdio.h>                 
                                   
int main()                         
{                                  
   int i=0;                        
   for(i=0; i< 2048; i++)          
   {                               
       if(i==1024) raise(SIGSEGV); 
       printf("x");                
   }                               
   return 0;                       
}

output:

Code:

> cc t.c
> ./a.out
Segmentation Fault(coredump)

Note -- NO output. Why? because the process did not flush stdout.

example2: using split, my version of split does not support -d:

Code:

> ./a.out | split -b 10m  -a 1 - "myappLog"                               
> ls -lrt | tail                                                          
-rw-r--r--   1 a     b        1799 Jan 11 11:53 WithSB_After_ChargeCalc.sql
-rw-rw-r--   1 a     b         329 Jan 11 11:53 after_estimates.txt        
-rw-r--r--   1 a     b         354 Jan 11 12:15 sql_threads.h              
drwxrwxr-x   2 a     b        2048 Jan 11 13:19 data                       
-rw-r--r--   1 a     b       22375 Jan 12 09:23 threadbud.pc               
-rw-r--r--   1 a     b        1384 Jan 12 09:28 ClearPrdgForLateMRE.sql    
-rw-------   1 a     b        7276 Jan 12 10:02 dead.letter                
-rw-r--r--   1 a     b         172 Jan 12 11:14 t.c                        
-rwxrwxr-x   1 a     b        6648 Jan 12 11:14 a.out                      
-rw-------   1 a     b      113228 Jan 12 11:19 core

No file produced.

example calling exit():

Code:

#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
void signal_handler(int sig)
{
	  exit(1);
	  
}

int main()
{
   int i=0;
    signal(SIGSEGV,signal_handler);
   for(i=0; i< 2048; i++) 
   {
       if(i==1024) raise(SIGSEGV);
       printf("x");
   }
   return 0;
}

output from exit():

Code:

appworx> ./a.out
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>

1023 bytes on stdout.

running thru split:

Code:

> ./a.out | split -b 10m  -a 1 - "myappLog"
> ls -lrt | tail
-rw-rw-r--   1 appworx  banner       329 Jan 11 11:53 after_estimates.txt
-rw-r--r--   1 appworx  banner       354 Jan 11 12:15 sql_threads.h
drwxrwxr-x   2 appworx  banner      2048 Jan 11 13:19 data
-rw-r--r--   1 appworx  banner     22375 Jan 12 09:23 threadbud.pc
-rw-r--r--   1 appworx  banner      1384 Jan 12 09:28 ClearPrdgForLateMRE.sql
-rw-------   1 appworx  banner      7276 Jan 12 10:02 dead.letter
-rw-------   1 appworx  banner    105004 Jan 12 11:26 core
-rw-r--r--   1 appworx  banner       277 Jan 12 11:27 t.c
-rwxrwxr-x   1 appworx  banner      6852 Jan 12 11:27 a.out
-rw-rw-r--   1 appworx  banner      1024 Jan 12 11:31 myappLoga

myapp is the problem not split. IMO.

jim mcnamara

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