Questions tagged [expansion]
428 questions
208
votes
6 answers
Base64: What is the worst possible increase in space usage?
If a server received a base64 string and wanted to check it's length before converting,, say it wanted to always permit the final byte array to be 16KB. How big could a 16KB byte array possibly become when converted to a Base64 string (assuming one…
700 Software
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48
votes
3 answers
Why does shell ignore quoting characters in arguments passed to it through variables?
These work as advertised:
grep -ir 'hello world' .
grep -ir hello\ world .
These don't:
argumentString1="-ir 'hello world'"
argumentString2="-ir hello\\ world"
grep $argumentString1 .
grep $argumentString2 .
Despite 'hello world' being enclosed by…
Ben Wilhelm
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39
votes
3 answers
how to make bash expand wildcards in variables?
I am trying achieve the same effect as typing
mv ./images/*.{pdf,eps,jpg,svg} ./images/junk/
at the command line, from inside a bash script. I have:
MYDIR="./images"
OTHERDIR="./images/junk"
SUFFIXES='{pdf,eps,jpg,svg}'
mv "$MYDIR/"*.$SUFFIXES…
Ross Duncan
- 610
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38
votes
4 answers
How to iterate through string one word at a time in zsh
How do I modify the following code so that when run in zsh it expands $things and iterates through them one at a time?
things="one two"
for one_thing in $things; do
echo $one_thing
done
I want the output to be:
one
two
But as written above,…
Rob Bednark
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32
votes
7 answers
Is it possible for C preprocessor macros to contain preprocessor directives?
I would like to do the equivalent of the following:
#define print_max(TYPE) \
# ifdef TYPE##_MAX \
printf("%lld\n", TYPE##_MAX); \
# endif
print_max(INT);
Now the #ifdef or any nested preprocessor directive is
not allowed as far as I can…
pixelbeat
- 30,615
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26
votes
5 answers
Curious C# using statement expansion
I've run ildasm to find that this:
using(Simple simp = new Simple())
{
Console.WriteLine("here");
}
generates IL code that is equivalent to this:
Simple simp = new Simple();
try
{
Console.WriteLine("here");
…
Matthew
- 261
- 3
- 3
25
votes
3 answers
Four Dollar signs in Makefile
I am reading the document of GNU Make. Here is an example
%.d: %.c
@set -e; rm -f $@; \
$(CC) -M $(CPPFLAGS) $< > $@.$$$$; \
sed ’s,\($*\)\.o[ :]*,\1.o $@ : ,g’ < $@.$$$$ > $@; \
rm -f $@.$$$$
I tried this on a C++ program,…
Tim
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24
votes
3 answers
bash variable expansion ${var:+"..."} in here-document removing double quotes?
I'm trying to understand why Bash removes double quotes (but not single quotes) when doing variable expansion with ${parameter:+word} (Use Alternate Value), in a here-document, for example:
% var=1
% cat < ${var:+"Hi there"}
> ${var:+'Bye'}
>…
Andreas Luik
- 241
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- 4
23
votes
3 answers
Why $'\0' or $'\x0' is an empty string? Should be the null-character, isn't it?
bash allows $'string' expansion. My man bash says:
Words of the form $'string' are treated specially.
The word expands to string, with backslash-escaped characters replaced as specified by the ANSI C standard.
Backslash escape sequences, if…
oHo
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22
votes
8 answers
Globbing/pathname expansion with colon as separator
How can I convert a string containing glob characters such as
/var/lib/gems/*/bin
into a colon-separated string of filenames (i.e. PATH compatible) matching the pattern?
i.e. echo /var/lib/gems/*/bin will return
/var/lib/gems/1.8/bin…
mjs
- 63,493
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- 122
21
votes
6 answers
Brace expansion in python glob
I have python 2.7 and am trying to issue:
glob('{faint,bright*}/{science,calib}/chip?/')
I obtain no matches, however from the shell echo {faint,bright*}/{science,calib}/chip? gives:
faint/science/chip1 faint/science/chip2 faint/calib/chip1…
astabada
- 1,029
- 4
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19
votes
5 answers
Gnuwin32 find.exe expands wildcard before performing search
I am using Gnuwin32 binaries on a Windows environment.
When I want to find files of a certain type, let's say PDF, I usually run:
find . -iname '*.pdf' -print
This works perfectly on any UNIX system.
find.exe . -iname "*.pdf" -print
But under…
Benoit
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18
votes
4 answers
Why zsh tries to expand * and bash does not?
I just encountered the following error with zsh when trying to use logcat.
Namely, when typing:
adb logcat *:D
I get the following error in zsh
zsh: no matches found: *:D
I have to escape the * like :
adb logcat \*:D
While using bash, I do…
Patryk
- 22,602
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17
votes
2 answers
android - so many problems with the expansion library
i need to use the new google-play (or market) expansion library , and i have hard time with it .
i wonder if anyone else is using it and notice the same problems i can see , so i would be very happy if you could help be to fix them:
1.sometimes i…
android developer
- 114,585
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17
votes
4 answers
bash tab completion without variable expansion?
Let's say I have these variables defined in my bashrc:
i='cgi-bin/internal';
e='cgi-bin/external';
f='cgi-bin/foo';
b='cgi-bin/bar';
ad='cgi-bin/admin';
#etc...
When I use the variable on the command line vim $i/edit_TAB it will expand…
Andrew Sohn
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