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How to find all serial devices (ttyS, ttyUSB, ..) on Linux without opening them?
...ll TTY devices but you might want to exclude those pesky virtual terminals and pseudo terminals. I suggest you examine only those which have a device/driver entry:
# ll /sys/class/tty/*/device/driver
lrwxrwxrwx 1 root root 0 2012-03-28 19:07 /sys/class/tty/ttyS0/device/driver -> ../../../bus/pnp...
Nullable Foreign Key bad practice?
...hat bad practice or would you rather work with a link table between Orders and Customers? Although the relationship is 1 to n, a link table would make it n to n. On the other hand, with a link table, I don't have those NULLS anymore...
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Chained method calls indentation style in Python [duplicate]
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The need for this style becomes more obvious as method names get longer and as methods start taking arguments:
return some_collection.get_objects(locator=l5) \
.get_distinct(case_insensitive=True) \
.filter(predicate=query(q5)) \
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Executing Shell Scripts from the OS X Dock?
... workflow with a single step - "Run Shell Script"
Then File > Save As, and change the File Format to "Application". When you open the application, it will run the Shell Script step, executing the command, exiting after it completes.
The benefit to this is it's really simple to do, and you can v...
How does database indexing work? [closed]
...a section for data, a pointer to the location of the next node (or block), and both need not be stored contiguously.
Due to the fact that a number of records can only be sorted on one field, we can state that searching on a field that isn’t sorted requires a Linear Search which requires N/2 block...
What are the minimum margins most printers can handle?
...ng real estate is a must but at the same time ensuring users printers can handle the tight margins is a must.
5 Answers
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Difference between shared objects (.so), static libraries (.a), and DLL's (.so)?
I have been involved in some debate with respect to libraries in Linux, and would like to confirm some things.
4 Answers
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What exactly does stringstream do?
I am trying to learn C++ since yesterday and I am using this document: http://www.cplusplus.com/files/tutorial.pdf (page 32) . I found a code in the document and I ran it. I tried inputting Rs 5.5 for price and an integer for quantity and the output was 0.
I tried inputting 5.5 and 6 and the output...
Why fragments, and when to use fragments instead of activities?
In Android API 11+, Google has released a new class called Fragment .
11 Answers
11
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Check Whether a User Exists
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You can also check user by id command.
id -u name gives you the id of that user.
if the user doesn't exist, you got command return value ($?)1
And as other answers pointed out: if all you want is just to check if the user exists, use if with id directly, as i...