https://www.vimgolf.com/challenges/9v006233d72d000000000219
Start file
#!/bin/bash
a = 5
b = 10
sum = $a + $b
echo $sum
mul = $a * $b
echo $mul
End file
#!/bin/bash
a=5
b=10
sum=$((a + b))
echo $sum
mul=$((a * b))
echo $mul
=================================
The keystroke in this problem was 26 but I only get 41.
The way I used it
:%s/ = /=/g
:%s/$a/$((a/g
:%s/$b/b))/g
I don't know how to reduce keystrokes more. Please give me some advice.
/g means "do the substitution on every match in the line". There is only one match for each pattern so the /gs are not necessary:
:%s/ = /=<CR>
:%s/$a/$((a<CR>
:%s/$b/b))<CR>
You are down to 36 keystrokes.
See :help :s_g.
In this specific case, $a + $b can be matched with a single pattern, $.*b, so you could fuse the two last substitutions into a single one:
:%s/ = /=<CR>
:%s/$.*b/$((&))<CR>
And you are down to 26 keystrokes.
See :help s/\&.
Related
when I do
$ ls | wc -l
703
It gave me the result 703, I want to print 702 (703-1)
How can I do it in bash?
You can use arithmetic expansion:
result=$(( $(ls | wc - l) - 1))
or just ignore one of the files
result=$(ls | tail -n+2 | wc -l)
Note that it doesn't work if filenames contain the newline character; use ls -q to get one filename per line in such a case. This applies to the first solution, too, if you're interested in the number of files and not the number of lines in their names.
(Cheeky answer) Remove one line from the output before counting :D
ls | sed '1d' | wc -l
How to convert result as Integer in bash
#choroba has already answered this question and it should have solved OP's problem. However, I want to add more to his answer.
The OP's wants to convert the result into Integer but Bash doesn't have any data type like Integer.
Unlike many other programming languages, Bash does not segregate its variables by "type." Essentially, Bash variables are character strings, but, depending on context, Bash permits arithmetic operations and comparisons on variables. The determining factor is whether the value of a variable contains only digits.
See this for arithmetic operation in Bash.
See this for a best example to learn the untyped nature of Bash. I have posted the example below:
#!/bin/bash
# int-or-string.sh
a=2334 # Integer.
let "a += 1"
echo "a = $a " # a = 2335
echo # Integer, still.
b=${a/23/BB} # Substitute "BB" for "23".
# This transforms $b into a string.
echo "b = $b" # b = BB35
declare -i b # Declaring it an integer doesn't help.
echo "b = $b" # b = BB35
let "b += 1" # BB35 + 1
echo "b = $b" # b = 1
echo # Bash sets the "integer value" of a string to 0.
c=BB34
echo "c = $c" # c = BB34
d=${c/BB/23} # Substitute "23" for "BB".
# This makes $d an integer.
echo "d = $d" # d = 2334
let "d += 1" # 2334 + 1
echo "d = $d" # d = 2335
echo
# What about null variables?
e='' # ... Or e="" ... Or e=
echo "e = $e" # e =
let "e += 1" # Arithmetic operations allowed on a null variable?
echo "e = $e" # e = 1
echo # Null variable transformed into an integer.
# What about undeclared variables?
echo "f = $f" # f =
let "f += 1" # Arithmetic operations allowed?
echo "f = $f" # f = 1
echo # Undeclared variable transformed into an integer.
#
# However ...
let "f /= $undecl_var" # Divide by zero?
# let: f /= : syntax error: operand expected (error token is " ")
# Syntax error! Variable $undecl_var is not set to zero here!
#
# But still ...
let "f /= 0"
# let: f /= 0: division by 0 (error token is "0")
# Expected behavior.
# Bash (usually) sets the "integer value" of null to zero
#+ when performing an arithmetic operation.
# But, don't try this at home, folks!
# It's undocumented and probably non-portable behavior.
# Conclusion: Variables in Bash are untyped,
#+ with all attendant consequences.
exit $?
Since yesterday I am facing with a strange behavior of shell code.
This is the code:
#!/bin/bash
operatori="/*-+="
temp=$1
len_temp=${#temp}
for (( i=0; i<$len_temp; i++ ))
do
array[i]=${temp:i:1}
#echo 'i= '${array[i]}
done
for i in ${array[#]}
do
if [[ "$operatori" =~ "$i" ]]; then
echo '##'$i
fi
done
It is executed with $1 = tom*jerry-1=0.
In this version of the code , i expect to return:
##*
##-
##=
But it returns just
##-
##=
On the other hand, I tried to deny the condition, having
if ! [[ "$operatori" =~ "$i" ]]; then
But the result is more strange:
##t
##o
##m
##analyzer.sh
##gnome-terminal.desktop
##mount location.sh
##test.sh
##j
##e
##r
##r
##y
##1
##0
Where I expect to receive:
##t
##o
##m
##j
##e
##r
##r
##y
##1
##0
where the analyzer.sh, gnome-teminal.desktop, mount location.sh, test.sh represents some files from the same location where my code is saved.
Can anyone tell me what am I doing wrong?
You should wrap variable references in double-quotes to prevent unexpected parsing oddities. In particular, use for i in "${array[#]}" and echo "##$i".
What's happening here is that in the for statement, the array expands to the equivalent of t o m * j e r r y - 1 = 0, which then undergoes word splitting (ok in this case) and wildcard expansion (which replaces the * with a list of files in the current directory), giving the equivalent of t o m analyzer.sh gnome-terminal.desktop 'mount location.sh' test.sh j e r r y - 1 = 0, which then causes the weird results you're seeing.
You could avoid this problem by setting the noglob shell option (as Kenavoz) suggested), but this will break any parts of the script that depend on wildcard expansion (and still leaves the potential for unexpected word splitting). It's better to just use double-quotes.
You can set bash to noglob as first command of your script to prevent globbing with * :
set -o noglob
Update :
Use set +o noglob to set noglob back to off when your script needs wildcard expansion :
set -o noglob
for i in ${array[#]}
do
if [[ "$operatori" =~ "$i" ]]; then
echo '##'$i
fi
done
set +o noglob
Note : #mikcutu, the noglob solution is a (working) workaround. See #Gordon Davisson's answer for details about why you first should double-quote your variables to prevent word splitting.
When I run commands in my shell as below, it returns an expr: non-integer argument error. Can someone please explain this to me?
$ x=20
$ y=5
$ expr x / y
expr: non-integer argument
Those variables are shell variables. To expand them as parameters to another program (ie expr), you need to use the $ prefix:
expr $x / $y
The reason it complained is because it thought you were trying to operate on alphabetic characters (ie non-integer)
If you are using the Bash shell, you can achieve the same result using expression syntax:
echo $((x / y))
Or:
z=$((x / y))
echo $z
I believe it was already mentioned in other threads:
calc(){ awk "BEGIN { print "$*" }"; }
then you can simply type :
calc 7.5/3.2
2.34375
In your case it will be:
x=20; y=3;
calc $x/$y
or if you prefer, add this as a separate script and make it available in $PATH so you will always have it in your local shell:
#!/bin/bash
calc(){ awk "BEGIN { print $* }"; }
Why not use let; I find it much easier.
Here's an example you may find useful:
start=`date +%s`
# ... do something that takes a while ...
sleep 71
end=`date +%s`
let deltatime=end-start
let hours=deltatime/3600
let minutes=(deltatime/60)%60
let seconds=deltatime%60
printf "Time spent: %d:%02d:%02d\n" $hours $minutes $seconds
Another simple example - calculate number of days since 1970:
let days=$(date +%s)/86400
Referencing Bash Variables Requires Parameter Expansion
The default shell on most Linux distributions is Bash. In Bash, variables must use a dollar sign prefix for parameter expansion. For example:
x=20
y=5
expr $x / $y
Of course, Bash also has arithmetic operators and a special arithmetic expansion syntax, so there's no need to invoke the expr binary as a separate process. You can let the shell do all the work like this:
x=20; y=5
echo $((x / y))
To get the numbers after decimal point, you can do this:-
read num1 num2
div=`echo $num1 / $num2 | bc -l`
echo $div
let's suppose
x=50
y=5
then
z=$((x/y))
this will work properly .
But if you want to use / operator in case statements than it can't resolve it.
In that case use simple strings like div or devide or something else.
See the code
I am trying to make a switch statement to work in tcsh but I am not sure why it is not working. I am displaying a menu on the screen and if the option is selected it shows the price and then goes back to the top and repeats until the exit option is selected.
#!/bin/csh
clear
echo -n "Petes A Pizza "
echo -n " Menu "
echo -n " "
echo -n " Make a selection "
echo -n " "
echo -n " A. Speciality Pizza "
echo -n " B. Veggi Lovers Pizza "
echo -n " C. Meat Lovers Pizza "
echo -n " D. Hawaiian Pizza "
echo -n " E. Cheese Pizza "
echo -n " F. Exit "
set a = $<
switch ($a)
case [A] :
set A = ((7.99 + 0.07))
echo $A
sleep 5
goto top
case [B] : #they choose option 2
set B = ((8.99 * 0.07) + 8.99)
echo $B
sleep 5
goto top
case [C] : #they choose option 3
set C = ((6.99 * 0.07) + 6.99)
echo $C
sleep 5
goto top
case [D] : #they choose option 4
set D = ((8.49 * 0.07) + 8.49)
echo $D
sleep 5
goto top
case [E] : #they choose option 5
set E = ((3.99 * 0.07) + 3.99)
echo $E
sleep 5
case [F] :
exit 0
breaksw
endsw
end
Here are a few suggestions that should be enough to help you get it working.
Change #!/bin/csh to #!bin/csh -f. This tells the shell not to read your ~/.cshrc file, which saves time and can avoid confusion. (If you accidentally write code that depends on aliases you've defined in your .cshrc, for example, your script won't work for anyone else.)
If you must clear the screen, the clear command is the way to do it -- but why? If I want to clear my screen before running your script, I'll do it myself, thank you very much. If I have information on my screen that I don't want to lose, I'll be annoyed when your script decides to erase it for me.
Change all the echo -ns to just echo. The -n option tells echo to print its output without a trailing newline; your entire menu will be printed on one line.
The square brackets in your case labels are unnecessary. case A : means the same thing as case [A] :. Note that you're requiring the user to provide input in upper case, which may be inconvenient.
set A = ((7.99 + 0.07))
...
set B = ((8.99 * 0.07) + 8.99)
These are inconsistent. It looks like you're trying to compute a base price plus 7% sales tax. For case B, a simpler expression for that is 8.99 * 1.07.
csh doesn't recognize this (( ... )) syntax; I wonder where you got the idea that it does. csh can do arithmetic using the # command:
# x = 2 + 2
# x ++
but it only operates on integers. The bc command can do floating-point calculations. You could write something like:
set B = `echo 'scale=5; 1.07 * 8.99' | bc`
Or, more simply:
set B = `echo '1.07 * 8.99' | bc -l
but bc -l may give you more digits than you want. man bc for more information on the bc command, its syntax, and how it works. Remember that the values of csh variables are strings, not numbers.
(I'm not sure bc is the best tool for this job.)
Finally, csh is not the best language for writing scripts. I've been using it for more years than I care to admit, and I sometimes have to resort to trial and error to find out how a given piece of syntax will behave; the syntax is poorly defined in many cases, and the man page doesn't always clear things up.
Suggested reading: "Csh Programming Considered Harmful", by Tom Christiansen.
I need to do some integer math in csh (and no, other shells are not an option, nor is bc, nor is perl, nor is python, period).
In bash my task would look like
seq 1 1 10 > m.txt #supplied from elsewhere
a=2 #supplied from elsewhere
b=3 #supplied from elsewhere
head -n $[$a*$b] m.txt # the line in question
then the question is Is there an expression in csh that computes $[$a*$b] inline?
I know that I can do # c = $a * $b in csh, but that's not inline. I did a little bit of googling and searching SO, but no success so far, so any help is greatly appreciated!
Are your use of square-brackets meant to indicate an array notation or matrix math? csh has no such built-in features.
ELSE, if you mean like bash $(($a * $b)), you can use csh cmd-substitution with backquotes to give you
head -n `expr $a \* $b` m.txt
Note that if your goal was to avoid spawning extra processes, this does not meet your goal, but it is "in-line"
Edit I see I mistyped as $( $a * $b ), see inline correction above.
IHTH.
Without using something outside of the shell, no.
The usual culprit for math from old school shell scripts is expr:
head -n `expr $a \* $b` m.txt
but if that's just as verboten as bc et al, then you're out of luck. Period.
Yes, but it's not pretty:
% seq 1 1 10 > m.txt
% set a = 2
% set b = 3
% head -n `# tmp = $a * $b ; echo $tmp ; unset tmp` m.txt
1
2
3
4
5
6
Note that this will clobber $tmp if you happen to have a variable of that name, so choose a unique name.
(Though I wonder why bc, perl, and python are not an option.)