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Bash tool to get nth line from a file
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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...
Split by comma and strip whitespace in Python
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Use list comprehension -- simpler, and just as easy to read as a for loop.
my_string = "blah, lots , of , spaces, here "
result = [x.strip() for x in my_string.split(',')]
# result is ["blah", "lots", "of", "spaces", "here"]
See: Python docs on List Comp...
C libcurl get output into a string
...de that passes a buffer struct string {*ptr; len} to the callback function and grows that buffer on each call using realloc().
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <curl/curl.h>
struct string {
char *ptr;
size_t len;
};
void init_string(s...
Padding characters in printf
...=60
pad=$(printf '%*s' "$padlimit")
pad=${pad// /-}
So the pad (padlimit and padlength) could be based on terminal width ($COLUMNS) or computed from the length of the longest data string.
Output:
a--------------------------------bbbbbbb
aa--------------------------------bbbbbb
aaaa--------------...
Inserting a Python datetime.datetime object into MySQL
...", 4, now))
With regards to the format, I had success with the above command (which includes the milliseconds) and with:
now.strftime('%Y-%m-%d %H:%M:%S')
Hope this helps.
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Why does GCC generate 15-20% faster code if I optimize for size instead of speed?
I first noticed in 2009 that GCC (at least on my projects and on my machines) have the tendency to generate noticeably faster code if I optimize for size ( -Os ) instead of speed ( -O2 or -O3 ), and I have been wondering ever since why.
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Escape a string for a sed replace pattern
...replacement string (escapes themselves, forward slash for end of statement and & for replace all):
ESCAPED_REPLACE=$(printf '%s\n' "$REPLACE" | sed -e 's/[\/&]/\\&/g')
# Now you can use ESCAPED_REPLACE in the original sed statement
sed "s/KEYWORD/$ESCAPED_REPLACE/g"
If you ever need t...
How to validate phone numbers using regex
...ogether a comprehensive regex to validate phone numbers. Ideally it would handle international formats, but it must handle US formats, including the following:
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How does the bitwise complement operator (~ tilde) work?
...representation of a number, taking its complement (inverting all the bits) and adding one. Two starts as 0000 0010, and by inverting the bits we get 1111 1101. Adding one gets us the result above. The first bit is the sign bit, implying a negative.
So let's take a look at how we get ~2 = -3:
Here's ...
How to comment out a block of Python code in Vim
...rst column of the first line you want to comment.
Step 2: Press: Ctrl+v and select the lines you want to comment:
Step 3: Shift-I#space (Enter Insert-at-left mode, type chars to insert. The selection will disappear, but all lines within it will be modified after Step 4.)
Step 4: Esc
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