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What's the better (cleaner) way to ignore output in PowerShell? [closed]

由 耗尽温柔 提交于 2019-12-17 02:24:24
问题 Closed . This question is opinion-based. It is not currently accepting answers. Want to improve this question? Update the question so it can be answered with facts and citations by editing this post. Closed 9 months ago . Let's say you have a method or a cmdlet that returns something, but you don't want to use it and you don't want to output it. I found these two ways: Add-Item > $null [void]Add-Item Add-Item | Out-Null What do you use? Which is the better/cleaner approach? Why? 回答1: I just

determine size of array if passed to function

由 故事扮演 提交于 2019-12-17 02:22:12
问题 Is it possible to determine the size of an array if it was passed to another function (size isn't passed)? The array is initialized like int array[] = { XXX } .. I understand that it's not possible to do sizeof since it will return the size of the pointer .. Reason I ask is because I need to run a for loop inside the other function where the array is passed. I tried something like: for( int i = 0; array[i] != NULL; i++) { ........ } But I noticed that at the near end of the array, array[i]

MySQL: selecting rows where a column is null

由 假装没事ソ 提交于 2019-12-17 02:07:15
问题 I'm having a problem where when I try to select the rows that have a NULL for a certain column, it returns an empty set. However, when I look at the table in phpMyAdmin, it says null for most of the rows. My query looks something like this: SELECT pid FROM planets WHERE userid = NULL Empty set every time. A lot of places said to make sure it's not stored as "NULL" or "null" instead of an actual value, and one said to try looking for just a space ( userid = ' ' ) but none of these have worked.

Does free(ptr) where ptr is NULL corrupt memory?

由 青春壹個敷衍的年華 提交于 2019-12-16 22:46:12
问题 Theoretically I can say that free(ptr); free(ptr); is a memory corruption since we are freeing the memory which has already been freed. But what if free(ptr); ptr=NULL; free(ptr); As the OS will behave in an undefined manner I cannot get an actual theoretical analysis for this about what's happening. Whatever I am doing, is this memory corruption or not? Is freeing a NULL pointer valid? 回答1: 7.20.3.2 The free function Synopsis #include <stdlib.h> void free(void *ptr); Description The free

/dev/null 2>&1 详解

由 匆匆过客 提交于 2019-12-16 21:37:03
【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>> 今天一个朋友突然在自己的维护的Linux中, /var/spool/cron/root 中看到了以下的内容: 30 19 * * * /usr/bin/**dcon.sh > /dev/null 2>&1 59 23 * * 1-7 /home/s**-log/squid-log.renew > /dev/null 2>&1 50 1 * * 1-7 /usr/local/src/**log.sh > /dev/null 2>&1 20 2 * * 1-7 /home/sq**-log/**log > /dev/null 2>&1 30 2 * * 1-7 /home/sq**-log/**log.01 30 22 * * * /bin/**sync > /dev/null 2>&1 00 8 * * 1-7 /home/**-log/rmcore > /dev/null 2>&1 00 16 * * 1-7 /home/**-log/rmcore > /dev/null 2>&1 他问我为什么要用 /dev/null 2>&1 这样的写法.这条命令的意思是将标准输出和错误输出全部重定向到/dev/null中,也就是将产生的所有信息丢弃.下面我就为大家来说一下, command > file 2>file 与

shell之“>/dev/null 2>&1”详解

由 送分小仙女□ 提交于 2019-12-16 21:13:30
【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>> 以下是本人的理解,大家看看对不对,欢迎讨论~ shell中可能经常能看到：>/dev/null 2>&1 命令的结果可以通过 %> 的形式来定义输出,其中 %> 代表文件描述符 我们将这个命令组合：“>/dev/null 2>&1” 拆为四部分来分析下: 1：首先 0> 表示stdin标准输入; 1> 表示stdout标准输出; 2> 表示stderr错误输出; 2：符号 > 等价于 1> (系统默认为1,省略了先); 所以">/dev/null"等同于 "1>/dev/null" 3：/dev/null 代表空设备文件 4：& 可以理解为是" 等同于 "的意思，2>&1，即表示2的输出重定向等同于1 因此，>/dev/null 2>&1 也可以写成“1> /dev/null 2> &1” 那么本文标题的语句执行过程为： 1>/dev/null ：首先表示标准输出重定向到空设备文件，也就是不输出任何信息到终端，说白了就是不显示任何信息。 2>&1 ：接着，将标准错误输出重定向 到 标准输出，因为之前标准输出已经重定向到了空设备文件，所以标准错误输出也重定向到空设备文件。 来源： oschina 链接： https://my.oschina.net/u/96486/blog/11514

How to check for an undefined or null variable in JavaScript?

由 给你一囗甜甜゛ 提交于 2019-12-16 20:05:54
问题 We are frequently using the following code pattern in our JavaScript code if (typeof(some_variable) != 'undefined' && some_variable != null) { // Do something with some_variable } Is there a less verbose way of checking that has the same effect? According to some forums and literature saying simply the following should have the same effect. if (some_variable) { // Do something with some_variable } Unfortunately, Firebug evaluates such a statement as error on runtime when some_variable is

Unity: Null while making new class instance

由 為{幸葍}努か 提交于 2019-12-16 19:55:44
问题 I got stuck in pretty dumb situation: I'm making new instance of the generic class but it returns "weird" null. Rule rule2 = new Rule(); // initiate the class Debug.Log(rule2); //1st debug rule2.RuleSetup(r: "CaughtEnough", li: 0); //setting up the parameters Debug.Log(rule2.rule); //2nd debug 1st debug gives me null UnityEngine.Debug:Log(Object) at the same time setting up the parameters works, and 2nd debug gives me CaughtEnough UnityEngine.Debug:Log(Object) which is what supposed to be in

IllegalArgumentException or NullPointerException for a null parameter? [closed]

由 时光总嘲笑我的痴心妄想 提交于 2019-12-16 19:51:56
问题 Closed . This question is opinion-based. It is not currently accepting answers. Want to improve this question? Update the question so it can be answered with facts and citations by editing this post. Closed 3 years ago . I have a simple setter method for a property and null is not appropriate for this particular property. I have always been torn in this situation: should I throw an IllegalArgumentException, or a NullPointerException? From the javadocs, both seem appropriate. Is there some

How to determine if variable is 'undefined' or 'null'?

由 假装没事ソ 提交于 2019-12-16 19:45:15
问题 How do I determine if variable is undefined or null ? My code is as follows: var EmpName = $("div#esd-names div#name").attr('class'); if(EmpName == 'undefined'){ //DO SOMETHING }; <div id="esd-names"> <div id="name"></div> </div> But if I do this, the JavaScript interpreter halts execution. 回答1: You can use the qualities of the abstract equality operator to do this: if (variable == null){ // your code here. } Because null == undefined is true, the above code will catch both null and undefined
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