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Adding a column to an existing table in a Rails migration
...ontaining line:
add_column :users, email, string
Then do a rake db:migrate and it'll run the new migration, creating the new column.
If you have not yet run the original migration you can just edit it, like you're trying to do. Your migration code is almost perfect: you just need to remove the add_...
How to get “wc -l” to print just the number of lines without file name?
outputs number of lines and file name.
9 Answers
9
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List Git aliases
... list of my git aliases, i.e., something analogous to the bash alias command?
16 Answers
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Show space, tab, CRLF characters in editor of Visual Studio
...ed > View White Space. The keyboard shortcut is CTRL+R, CTRL+W. The command is called Edit.ViewWhiteSpace.
It works in all Visual Studio versions at least since Visual Studio 2010, the current one being Visual Studio 2019 (at time of writing). In Visual Studio 2013, you can also use CTRL+E, S or...
Converting from a string to boolean in Python?
...ref.html#distutils.util.strtobool
True values are y, yes, t, true, on and 1; false values are n, no, f, false, off and 0. Raises ValueError if val is anything else.
Be aware that distutils.util.strtobool() returns integer representations and thus it needs to be wrapped with bool() to get Bool...
How to check if object has any properties in JavaScript?
...ws:
for(var prop in ad) {
if (ad.hasOwnProperty(prop)) {
// handle prop as required
}
}
It is important to use the hasOwnProperty() method, to determine whether the object has the specified property as a direct property, and not inherited from the object's prototype chain.
Edit
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Bash tool to get nth line from a file
...
head and pipe with tail will be slow for a huge file. I would suggest sed like this:
sed 'NUMq;d' file
Where NUM is the number of the line you want to print; so, for example, sed '10q;d' file to print the 10th line of file.
Ex...
Apache redirect to another port
I've struggled with this for some time and am definitely doing something wrong.
14 Answers
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How can I inspect disappearing element in a browser?
...element that contains the disappearing element. Right click on the element and apply "Break on... > Subtree Modifications." This will throw a debugger pause before the element disappears, which will allow you to interact with the element in a paused state.
Update Oct 22 2019: with the release of...
What are the differences between vector and list data types in R?
What are the main differences between vector and list data types in R? What are the advantages or disadvantages of using (or not) these two data types?
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