Linux and UNIX Man Pages

Linux & Unix Commands - Search Man Pages

dispatch_once(3) [osx man page]

dispatch_once(3)					   BSD Library Functions Manual 					  dispatch_once(3)

NAME
dispatch_once -- execute a block only once SYNOPSIS
#include <dispatch/dispatch.h> void dispatch_once(dispatch_once_t *predicate, void (^block)(void)); void dispatch_once_f(dispatch_once_t *predicate, void *context, void (*function)(void *)); DESCRIPTION
The dispatch_once() function provides a simple and efficient mechanism to run an initializer exactly once, similar to pthread_once(3). Well designed code hides the use of lazy initialization. For example: FILE *getlogfile(void) { static dispatch_once_t pred; static FILE *logfile; dispatch_once(&pred, ^{ logfile = fopen(MY_LOG_FILE, "a"); }); return logfile; } FUNDAMENTALS
The dispatch_once() function is a wrapper around dispatch_once_f(). SEE ALSO
dispatch(3) Darwin May 1, 2009 Darwin

Check Out this Related Man Page

dispatch_after(3)					   BSD Library Functions Manual 					 dispatch_after(3)

NAME
dispatch_after -- schedule blocks for deferred execution SYNOPSIS
#include <dispatch/dispatch.h> void dispatch_after(dispatch_time_t when, dispatch_queue_t queue, void (^block)(void)); void dispatch_after_f(dispatch_time_t when, dispatch_queue_t queue, void *context, void (*function)(void *)); DESCRIPTION
The dispatch_after() function submits the block to the given queue at the time specified by the when parameter. The when parameter is a value created by dispatch_time() or dispatch_walltime(). For a more detailed description about submitting blocks to queues, see dispatch_async(3). CAVEATS
dispatch_after() retains the passed queue. Specifying DISPATCH_TIME_NOW as the when parameter is supported, but is not as efficient as calling dispatch_async(). The result of passing DISPATCH_TIME_FOREVER as the when parameter is undefined. FUNDAMENTALS
The dispatch_after() function is a wrapper around dispatch_after_f(). SEE ALSO
dispatch(3), dispatch_async(3), dispatch_time(3) Darwin May 1, 2009 Darwin
Man Page

13 More Discussions You Might Find Interesting

1. AIX

AIX Links

Manufacturer Links General Information Home Page: IBM United States Documentation/Information: IBM System p - UNIX servers: Support and services pSeries and AIX Information Center Developerworks AIX Wiki: AIX Wiki AIX for System Administrators In-depth information from IBM: IBM... (0 Replies)
Discussion started by: Perderabo
0 Replies

2. OS X (Apple)

Mac OS X: Based on UNIX - Solid As a Rock

See this threads: Page Not Found - Apple Open Source - Apple (0 Replies)
Discussion started by: Neo
0 Replies

3. Shell Programming and Scripting

At A Glance Coloured Real Time Bargraph Generator...

Not sure if anyone is interested but I am just getting into UNIX like shell scripting... I have great interest in pseudo-animations in text mode and accessing HW like /dev/dsp for example... ... Have fun, I do... ;o) # !/bin/sh # # Bargraph_Generator.sh # # A DEMO 6 bit coloured... (0 Replies)
Discussion started by: wisecracker
0 Replies

4. UNIX for Advanced & Expert Users

When is a _function_ not a _function_?

For a starter I know the braces are NOT in the code... Consider these code snippets:- #!/bin/bash --posix x=0 somefunction() if then echo "I am here." fi # somefunction #!/bin/bash --posix x=0 somefunction() if (2 Replies)
Discussion started by: wisecracker
2 Replies

5. OS X (Apple)

Installing Dash Shell on OS X Lion

For those interested in installing dash shell on OSX Lion to help test POSIX compliancy of shell scripts, it is quite easy. I did it like this: If you don't have gcc on your system: 0. Download and install the Command Line Tools for Xcode package from Sign In - Apple * 1. Download the dash... (2 Replies)
Discussion started by: Scrutinizer
2 Replies

6. OS X (Apple)

Hearing Aid for OSX 10.12.x and greater.

Hearing Aid... Hi folks yet another bizarre piece of code that is Apple OSX 10.12.x to at least 10.14.1 specific. It requires only a default OSX install, and the internal microphone along with an external headphone assembly. Pre-amble, 14-02-2019: For over 3 weeks now I have been suffering a... (3 Replies)
Discussion started by: wisecracker
3 Replies

7. UNIX for Advanced & Expert Users

Shopt -s histappend

What is the point of this? Whenever I close my shell it appends to the history file without adding this. I have never seen it overwrite my history file. # When the shell exits, append to the history file instead of overwriting it shopt -s histappend (3 Replies)
Discussion started by: cokedude
3 Replies

8. OS X (Apple)

Undeletable file

Greetings, I'm trying to delete a file with a weird name from within Terminal on a Mac. It's a very old file (1992) with null characters in the name: ␀␀Word Finder® Plus™. Here are some examples of what I've tried: 12FX009:5 dpontius$ ls ␀␀Word Finder® Plus™ 12FX009:5 dpontius$ rm... (29 Replies)
Discussion started by: dpontius
29 Replies

9. Shell Programming and Scripting

To print diamond asterisk pattern based on inputs

I have to print the number of stars that increases on each line from the minimum number until it reaches the maximum number, and then decreases until it goes back to the minimum number. After printing out the lines of stars, it should also print the total number of stars printed. I have tried... (13 Replies)
Discussion started by: rohit_shinez
13 Replies

10. Programming

My first PERL incarnation... Audio Oscillograph

Hi all... Well guys and gals, I jumped in at the deep end and found things that PERL cannot do by default. Many tricky terminal escape codes are not catered for so I had to create workarounds. One thing I searched for was this: Passing perl variable to shell command AND, @Neo this was... (15 Replies)
Discussion started by: wisecracker
15 Replies

11. Shell Programming and Scripting

A dash to GOTO or a dash from GOTO, that is the question...

Well, guys I saw a question about GOTO for Python. So this gave me the inspiration to attempt a GOTO function for 'dash', (bash and ksh too). Machine: MBP OSX 10.14.3, default bash terminal, calling '#!/usr/local/bin/dash'... This is purely a fun project to see if it is possible in PURE... (3 Replies)
Discussion started by: wisecracker
3 Replies

12. Shell Programming and Scripting

Syntax error in subtraction in Bash

I am sharing a code snippet. for (( i=0; i<=$(( $count -1 )); i++ )) do first=${barr2} search=${barr1} echo $first echo "loop begins" for (( j=0; j<=5000; j++ )) do if } == $search ]]; then echo $j break; fi done second=${harr2} echo $second (2 Replies)
Discussion started by: ngabrani
2 Replies

13. Shell Programming and Scripting

Python: Refer a properties file from different location

Hi All, I'm having a python script: test.py in /path/to/script/test.py I'm using a properties file: test_properties.py (it is having values as dictionary{}) which is in same DIR as the script. Sample Properties file: params = { 'target_db' : 'a1_db' 'src_db' : ... (15 Replies)
Discussion started by: saps19
15 Replies

Featured Tech Videos