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How to check if a Unix .tar.gz file is a valid file without uncompressing?
...mple of failed tar ball test...
$ echo "this will not pass the test" > hello.tgz
$ tar -xvzf hello.tgz -O > /dev/null
gzip: stdin: not in gzip format
tar: Child returned status 1
tar: Error exit delayed from previous errors
$ rm hello.*
Working Example...
$ ls hello*
ls: hello*: No such fi...
Assign multiple columns using := in data.table, by group
...t!
x <- data.table(a = 1:3, b = 1:6)
f <- function(x) {list("hi", "hello")}
x[ , c("col1", "col2") := f(), by = a][]
# a b col1 col2
# 1: 1 1 hi hello
# 2: 2 2 hi hello
# 3: 3 3 hi hello
# 4: 1 4 hi hello
# 5: 2 5 hi hello
# 6: 3 6 hi hello
x[ , c("mean", "sum") := list(mea...
How to pass parameters in $ajax POST?
... url as parameters, but if I set them directly to the url using /?field1="hello" it works.
9 Answers
...
OS detecting makefile
...d on five files
├── lib
│ └── Makefile
│ └── hello.h
│ └── hello.c
└── app
└── Makefile
└── main.c
Reminder: Makefile is indented using tabulation. Caution when copy-pasting below sample files.
The two Makefile files
1. lib/Ma...
What does the 'static' keyword do in a class?
...ce members. In the example given, main does not know which instance of the Hello class (and therefore which instance of the Clock class) it should refer to. static members can only refer to static members. Instance members can, of course access static members.
Side note: Of course, static members c...
What is the purpose of .PHONY in a Makefile?
...a directory 'test' following files are present:
prerit@vvdn105:~/test$ ls
hello hello.c makefile
In makefile a rule is defined as follows:
hello:hello.c
cc hello.c -o hello
Now assume that file 'hello' is a text file containing some data, which was created after 'hello.c' file. So the mo...
How do I use grep to search the current directory for all files having the a string “hello” yet disp
... search the current directory for any and all files containing the string "hello" and display only .h and .cc files?
8 Answ...
How do you create different variable names while in a loop? [duplicate]
...dictionary:
d = {}
for x in range(1, 10):
d["string{0}".format(x)] = "Hello"
>>> d["string5"]
'Hello'
>>> d
{'string1': 'Hello',
'string2': 'Hello',
'string3': 'Hello',
'string4': 'Hello',
'string5': 'Hello',
'string6': 'Hello',
'string7': 'Hello',
'string8': 'Hello',...
Where does 'Hello world' come from?
' hello, world ' is usually the first example for any programming language. I've always wondered where this sentence came from and where was it first used.
...
Immutability of Strings in Java
...
str is not an object, it's a reference to an object. "Hello" and "Help!" are two distinct String objects. Thus, str points to a string. You can change what it points to, but not that which it points at.
Take this code, for example:
String s1 = "Hello";
String s2 = s1;
// s1 and ...