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Full Discussion: Unix shell scripting
Top Forums Shell Programming and Scripting Unix shell scripting Post 302074366 by azrealhk on Tuesday 23rd of May 2006 12:19:16 AM
Old 05-23-2006
I have seen ls, wc etc give false readings if the file is opened by another program which is writing to it.

if the output is not flushed then file size etc remains the same.
try....

# cat flush.pl
#!/usr/local/bin/perl
open FH, ">flush.txt";
for (1..410) {
print FH "abcdefg89\n";
}
sleep 360;
close FH;

NOTE: The string is 10 chars (including \n), 410 lines written before sleep. therefore size should be 4100 bytes. The file is already open and not close yet on the sleep.

# tail flush.txt
abcdefg89
abcdefg89
abcdefg89
abcdefg89
abcdefg89
abcdefg89
abcdefg89
abcdefg89
abcdefg89
abcdefg89
abcdef

The block size of our system is 4096 so instead of 4100 bytes, 4096 is seen. The tail command will only show upto 4096 bytes.

# ls -l flush.txt
-rw-r--r-- 1 root system 4096 May 23 12:06 flush.txt

Ls confirms only 4096 bytes is seen

# wc -l flush.txt
409 flush.txt

wc -l shows only 409 and note 410.

The file will only show 4100 when you close the file.

# ls -l flush.txt
-rw-r--r-- 1 root system 4100 May 23 12:18 flush.txt
 

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MONGO(1)							  Mongo Database							  MONGO(1)

NAME
mongo - the Mongo command-line tool SYNOPSIS
mongo [OPTIONS] [DB_ADDRESS] [FILE+] DESCRIPTION
mongo is a JavaScript shell (with GNU readline capabilities). It supports interactive and non-interactive use. When used interactively, JavaScript can be used to query the database or perform any other function normally available with SpiderMonkey. Database output is dis- played in JSON format. If JavaScript files are specified on the command line, the shell will run non-interactively, running each one in sequence and then exiting. EXAMPLES
mongo start the shell, connecting to the server at localhost:27017 and using the test database mongo foo start the shell using the foo database at localhost:27017 mongo 192.169.0.5/foo start the shell using the foo database at 192.169.0.5:27017 mongo 192.169.0.5:9999/foo start the shell using the foo database at 192.169.0.5:9999 mongo script1.js script2.js script3.js run three scripts and exit OPTIONS
--shell run the shell after executing files --help show usage information --host HOST server to connect to (default HOST=localhost) --port PORT port to connect to (default PORT=27017) --nodb do not connect to mongod --eval SCRIPT evaluate JavaScript -u USERNAME specify user to log in as -pPASSWORD specify password of user (notice there is no space) COPYRIGHT
Copyright 2007-2009 10gen SEE ALSO
For more information, please refer to the MongoDB wiki, available at http://www.mongodb.org. AUTHOR
Kristina Chodorow 10gen June 2009 MONGO(1)
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