03-02-2006
You're right about closing the file, my bad. However - 256 appears arbitrary. It is not.
Whatever file record length he/she expects, best practice dictates using a variable that is decalred to be significantly larger.
However - and don't get me going on this - picking lengths that are just one char longer than the record leads to trouble in production systems, if the program deals with data derived from any external source. And the memory savings is not worth the cost of debugging and fixing it later on, because some users did not follow procedures.
If you're worried about memory, which, within reason, is basically not merited except in embedded systems or realtime processing, check your requirements. I seldom see - "must run in less than 10MB of memory" - as a stipulated requirement. It's the same issue as using floats instead of doubles because it "saves memory" or "is faster".
The "is faster" is debatable, and is hardware dependant, plus floats are often promoted to doubles. The "saves memory" is usually correct except that what you gain is not worth what you lose - 9 digits of precision.
10 More Discussions You Might Find Interesting
1. Solaris
I want to have a permanent file created - and limit the size that this file can grow.. I want a circular file..
ie max size of file is 10 mb.. and if any new data written to file the oldest data removed..
How can I do this?
I am on solaris 9 x86 (3 Replies)
Discussion started by: frustrated1
3 Replies
2. AIX
Can anybody help me?
How to increase file size limit in aix 5.2? I have already specified in /etc/security/limits file :
default:
fsize = -1
core = 2097151
cpu = -1
data = -1
rss = -1
stack = -1
nofiles = 2000 (2 Replies)
Discussion started by: vjm
2 Replies
3. UNIX for Advanced & Expert Users
Hi,
I have a problem writing or copying a file 2GB or larger to either the second or third disk on my C8000. I've searched this forum and found some good information on this but still nothing to solve the problem.
I'm running hpux 11i, JFS3.3 and disk version 4 (from fstyp) on all 3 disks.
... (2 Replies)
Discussion started by: HaidoodFaulkauf
2 Replies
4. UNIX for Dummies Questions & Answers
Would appreciate some help, system was displaying an error regarding the kernal when a "sar" was run, after a reboot we get "WARNING user login limit exceeded by 1 user". We have plenty of licences. any ideas? (1 Reply)
Discussion started by: nchrocc
1 Replies
5. Solaris
Can you help. My server sunning solaris 9 on x86 platform pretty much hung for a few hours... I could not use telnet or ssh to the box - it kept refusing connection. A few hours later - I was able to log in again.
The server has not rebooted but here are the first errors in the messages log... (5 Replies)
Discussion started by: frustrated1
5 Replies
6. UNIX for Dummies Questions & Answers
Hello -
O/S is UnixWare 7.1.4
My prefered method of copying files between servers is 'rcp', which does not recognize symbolic links; therefore, files are duplicated many times over.
To avoid this duplication, I would like to use 'tar' and/or 'cpio' and pipe them through 'rcp', but... (1 Reply)
Discussion started by: rm -r *
1 Replies
7. Shell Programming and Scripting
Hi,
How to write a script which checks the size of a log file?
I want that the log file contents to get cleared as soon as it increases 1 KB.
Thanks (3 Replies)
Discussion started by: skyineyes
3 Replies
8. UNIX for Advanced & Expert Users
hi,
how can I find out what the limit of a file size is on unix?
thanks (6 Replies)
Discussion started by: JamesByars
6 Replies
9. Shell Programming and Scripting
Hi
I have many problems with a script. I have a script that formats a text file but always prints the same error when i try to execute it
The code is that:
{
if (NF==17){
print $0
}else{
fields=NF;
all=$0;
while... (2 Replies)
Discussion started by: fate
2 Replies
10. UNIX for Dummies Questions & Answers
Hello Everyone,
I am new to this forum and also unix/linux. Our application today threw an alert whcih read as
"The users active count on host has crossed the threshold limit of 50
and is standing at 65."
This was although cleared when I restarted tomcat. But I am not sure why this count... (0 Replies)
Discussion started by: ykhati
0 Replies
LEARN ABOUT OPENDARWIN
getrlimit
GETRLIMIT(2) BSD System Calls Manual GETRLIMIT(2)
NAME
getrlimit, setrlimit -- control maximum system resource consumption
SYNOPSIS
#include <sys/types.h>
#include <sys/time.h>
#include <sys/resource.h>
int
getrlimit(int resource, struct rlimit *rlp);
int
setrlimit(int resource, const struct rlimit *rlp);
DESCRIPTION
Limits on the consumption of system resources by the current process and each process it creates may be obtained with the getrlimit() call,
and set with the setrlimit() call.
The resource parameter is one of the following:
RLIMIT_CORE The largest size (in bytes) core file that may be created.
RLIMIT_CPU The maximum amount of cpu time (in seconds) to be used by each process.
RLIMIT_DATA The maximum size (in bytes) of the data segment for a process; this defines how far a program may extend its break with the
sbrk(2) system call.
RLIMIT_FSIZE The largest size (in bytes) file that may be created.
RLIMIT_MEMLOCK The maximum size (in bytes) which a process may lock into memory using the mlock(2) function.
RLIMIT_NOFILE The maximum number of open files for this process.
RLIMIT_NPROC The maximum number of simultaneous processes for this user id.
RLIMIT_RSS The maximum size (in bytes) to which a process's resident set size may grow. This imposes a limit on the amount of physical
memory to be given to a process; if memory is tight, the system will prefer to take memory from processes that are exceeding
their declared resident set size.
RLIMIT_STACK The maximum size (in bytes) of the stack segment for a process; this defines how far a program's stack segment may be
extended. Stack extension is performed automatically by the system.
A resource limit is specified as a soft limit and a hard limit. When a soft limit is exceeded a process may receive a signal (for example,
if the cpu time or file size is exceeded), but it will be allowed to continue execution until it reaches the hard limit (or modifies its
resource limit). The rlimit structure is used to specify the hard and soft limits on a resource,
struct rlimit {
rlim_t rlim_cur; /* current (soft) limit */
rlim_t rlim_max; /* hard limit */
};
Only the super-user may raise the maximum limits. Other users may only alter rlim_cur within the range from 0 to rlim_max or (irreversibly)
lower rlim_max.
An ``infinite'' value for a limit is defined as RLIM_INFINITY.
Because this information is stored in the per-process information, this system call must be executed directly by the shell if it is to affect
all future processes created by the shell; limit is thus a built-in command to csh(1) and ulimit is the sh(1) equivalent.
The system refuses to extend the data or stack space when the limits would be exceeded in the normal way: a break call fails if the data
space limit is reached. When the stack limit is reached, the process receives a segmentation fault (SIGSEGV); if this signal is not caught
by a handler using the signal stack, this signal will kill the process.
A file I/O operation that would create a file larger that the process' soft limit will cause the write to fail and a signal SIGXFSZ to be
generated; this normally terminates the process, but may be caught. When the soft cpu time limit is exceeded, a signal SIGXCPU is sent to
the offending process.
RETURN VALUES
A 0 return value indicates that the call succeeded, changing or returning the resource limit. A return value of -1 indicates that an error
occurred, and an error code is stored in the global location errno.
ERRORS
Getrlimit() and setrlimit() will fail if:
[EFAULT] The address specified for rlp is invalid.
[EPERM] The limit specified to setrlimit() would have raised the maximum limit value, and the caller is not the super-user.
SEE ALSO
csh(1), sh(1), quota(2), sigaction(2), sigaltstack(2), sysctl(3)
HISTORY
The getrlimit() function call appeared in 4.2BSD.
4th Berkeley Distribution June 4, 1993 4th Berkeley Distribution