Hi I'm looking to write a simple script which takes an input letter and outputs it's numerical equivalent :-
I was thinking of listing all letters as variables, then have bash read the input as a variable but from here I'm pretty stuck, any help would be awesome!
#!/bin/bash
echo "enter letter"
read "LET"
a=1
b=2
c=3
d=4
e=5
f=6
g=7
h=8
i=9
j=10
k=11
l=12
m=13
n=14
o=15
p=16
q=17
r=18
s=19
t=20
u=21
v=22
w=23
x=24
y=25
z=26
LET=${a..z}
if
$LET = [ ${a..z} ];
then
echo $NUM
sleep 5
echo "success!"
sleep 1
exit
else
echo "FAIL :("
exit
fi
Try this:
echo "Input letter"
read letter
result=$(($(printf "%d\n" \'$letter) - 65))
echo $result
0
ASCII equivalent of 'A' is 65 so all you've got to do to is to take away 65 (or 64, if you want to start with 1, not 0) from the letter you want to check. For lowercase the offset will be 97.
A funny one, abusing Bash's radix system:
read -n1 -p "Type a letter: " letter
if [[ $letter = [[:alpha:]] && $letter = [[:ascii:]] ]]; then
printf "\nCode: %d\n" "$((36#$letter-9))"
else
printf "\nSorry, you didn't enter a valid letter\n"
fi
The interesting part is the $((36#$letter-9)). The 36# part tells Bash to understand the following string as a number in radix 36 which consists of a string containing the digits and letters (case not important, so it'll work with uppercase letters too), with 36#a=10, 36#b=11, …, 36#z=35. So the conversion is just a matter of subtracting 9.
The read -n1 only reads one character from standard input. The [[ $letter = [[:alpha:]] && $letter = [[:ascii:]] ]] checks that letter is really an ascii letter. Without the [[:ascii:]] test, we would validate characters like é (depending on locale) and this would mess up with the conversion.
use these two functions to get chr and ord :
chr() {
[ "$1" -lt 256 ] || return 1
printf "\\$(printf '%03o' "$1")"
}
ord() {
LC_CTYPE=C printf '%d' "'$1"
}
echo $(chr 97)
a
USing od and tr
echo "type letter: "
read LET
echo "$LET" | tr -d "\n" | od -An -t uC
OR using -n
echo -n "$LET" | od -An -t uC
If you want it to start at a=1
echo $(( $(echo -n "$LET" | od -An -t uC) - 96 ))
Explanation
Pipes into the tr to remove the newline.
Use od to change to unsigned decimal.
late to the party: use an associative array:
# require bash version 4
declare -A letters
for letter in {a..z}; do
letters[$letter]=$((++i))
done
read -p "enter a single lower case letter: " letter
echo "the value of $letter is ${letters[$letter]:-N/A}"
Related
I am creating a function that will accept an input and determine if the value is a certain type of hash encoding (md5, sha1, sha256, and sha512). I have asked a few classmates and logically it makes sense, but clearly something is wrong.
#!/usr/bin/bash
function identify-hash() {
encryptinput=$(echo $1 | grep -E -i '^[a-z0-9=]+${32}')
if [[ -n $encryptinput ]]; then
echo "The $1 is a valid md5sum string"
exit
else
encryptinput=$(echo $1 | grep -E -i '^[a-z0-9=]+${40}')
if [[ -n $encryptinput ]]; then
echo "The $1 is a valid sha1sum string"
exit
else
encryptinput=$(echo $1 | grep -E -i '^[a-z0-9=]+${64}')
if [[ -n $encryptinput ]]; then
echo "The $1 is a valid sha256sum string"
exit
else
encryptinput=$(echo $1 | grep -E -i '^[a-z0-9=]+${128}')
if [[ -n $encryptinput ]]; then
echo "The $1 is a valid sha512sum string"
exit
else
echo "Unable to determine the hash function used to generate the input"
fi
fi
fi
fi
}
identify-hash $1
I know that hashes have a specific number of characters for them, but I don't know exactly why it's not working. Removing the {32} out of line 4 allows it to answer as a md5sum, but than it assumes everything is md5sum.
Suggestions?
Fixed your script. I advise you would have spotted most of the issues if you had used ShellCheck:
#!/usr/bin/env bash
identify_hash() {
# local variables
local -- encrypt_input
local -- sumname
# Regex capture the hexadecimal digits
if [[ "$1" =~ ([[:xdigit:]]+) ]]; then
encrypt_input="${BASH_REMATCH[1]}"
else
encrypt_input=''
fi
# Determine name of sum algorithm based on length of encrypt_input
case "${#encrypt_input}" in
32) sumname=md5sum ;;
40) sumname=sha1sum ;;
64) sumname=sha256sum ;;
128) sumname=sha512sum ;;
*) sumname=;;
esac
# If sum algorithm name found (sumname is not empty)
if [ -n "$sumname" ]; then
printf 'The %s is a valid %s string\n' "$encrypt_input" "$sumname"
else
printf 'Unable to determine the hash function used to generate the input\n' >&2
exit 1
fi
}
identify_hash "$1"
Something shorter, using bash:
checkHash() {
local -ar sumnames=([32]=md5sum [40]=sha1sum [64]=sha256sum [128]=sha512sum)
[[ "$1" =~ [[:xdigit:]]{32,129} ]]
echo "${sumnames[${#BASH_REMATCH}]+String $BASH_REMATCH could be }${sumnames[
${#BASH_REMATCH}]:-No hash tool match this string.}"
}
This will extract [:xdigit:] part out of any complete line:
checkHash 'Filename: 13aba32dbe4db7a7117ed40a25c29fa8 --'
String 13aba32dbe4db7a7117ed40a25c29fa8 could be md5sum
checkHash a32dba32dbe4db7a7117ed40a25c29fa8e4db7a7117ed40a25c29fa8
No hash tool match this string.
checkHash a32dba32dbe4db7a7117ed40a25c29fa8e4db7a7117ed40a25c29fa8da921adb
String a32dba32dbe4db7a7117ed40a25c29fa8e4db7a7117ed40a25c29fa8da921adb could be sha256sum
... then ${var+return this only if $var exist}
... and ${var:-return this if $var is empty}
Further explaining #Gordon Davissons' comment and some basics for anyone who stops by
NB This answer is extremely simplified to apply only to the current question. here's my preferred guide for more regex
Basics of regex
^ - start of a line
$ - end of a line
[...] - list of possible characters
has special sauce
a-z = all lowercase (English) letters; 0-9 = all digits; etc.
also accepts character classes - e.g [:xdigit:] for hexadecimal characters
the expression is now [[:xdigit:]] - i.e [:class:] inside [...]
{...} - number of times the preceding expression should be matched
^[a]{1}$ will match a but not aa
^f[o]{2}d$ will match food but not fod, foood, fooo*d
^[a-z]{4}$ will match
ball ✔️ but not buffalo ❌
cove ✔️ but not cover ❌
basically any line ( because of the ^...$) containing a string of exactly 4 (English) alphabetic characters
{1,5} - at least 1 and at most 5
* - shorthand for {0,} meaning 0 or any number of times
+ - shorthand for {1,} meaning at least 1; but no upper limit
? - shorthand for {1}
So ${32} is looking for 32 "end of line" \n in jargon and what you need is [a-z0-9=]{32} instead
BUT as also pointed out by Andrej Podzimek in the comments you need to match only hexadecimal [0-9a-f] characters which is the same as [:xdigit:]. Either can be used.
PS
more Basics
. (fullstop/period) matches ANY character including spaces and special characters
(...) is to match patterns
[a-z ]*(chicken).*
will match anything from chicken coop to chicken soup and please pass that chicken cookbook, Alex?
[.] means period/fullstop not any character
note the space after z this is to make space (ascii 32 ) a possible character
and . is case-insensituve
PPS if it's for homework/assignment/schoolwork, please specify so in your question :)
How to convert the alternative character of a string passed to script, if it is lower then it should be converted to upper and if it is upper then to lower??
read -p " Enter string" str
for i in `seq 0 ${#str}`
do
#echo $i
rem=$(($i % 2 ))
if [ $rem -eq 0 ]
then
echo ${str:$i:1}
else
fr=${str:$i:1}
if [[ "$fr" =~ [A-Z] ]]
then
echo ${str:$i:1} | tr '[:upper:]' '[:lower:]'
elif [[ "$fr" =~ [a-z] ]]
then
echo ${str:$i:1} | tr '[:lower:]' '[:upper:]'
else
echo ""
fi
fi
done
Your question is a bit challenging given that it is tagged shell and not as a question pertaining to an advanced shell like bash or zsh. In POSIX shell, you have no string indexes, no C-style for loop, and no [[ .. ]] operator to use character class pattern matching.
However, with a bit of awkward creativity, the old expr and POSIX string and arithmetic operations, and limiting your character strings to ASCII characters, you can iterate over a string changing uppercase to lowercase and lowercase and uppercase while leaving all other characters unchanged.
I wouldn't recommend the approach if you have an advanced shell available, but if you are limited to POSIX shell, as your question is tagged, it will work, but don't expect it to be super-fast...
#!/bin/sh
a=${1:-"This Is My 10TH String"} ## input and output strings
b=
i=1 ## counter and string length
len=$(expr length "$a")
asciiA=$(printf "%d" "'A") ## ASCII values for A,Z,a,z
asciiZ=$(printf "%d" "'Z")
asciia=$(printf "%d" "'a")
asciiz=$(printf "%d" "'z")
echo "input : $a" ## output original string
while [ "$i" -le "$len" ]; do ## loop over each character
c=$(expr substr "$a" "$i" "1") ## extract char from string
asciic=$(printf "%d" "'$c") ## convert to ASCII value
## check if asciic is [A-Za-z]
if [ "$asciiA" -le "$asciic" -a "$asciic" -le "$asciiZ" ] ||
[ "$asciia" -le "$asciic" -a "$asciic" -le "$asciiz" ]
then ## toggle the sign bit (bit-6)
b="${b}$(printf "\x$(printf "%x" $((asciic ^ 1 << 5)))\n")"
else
b="$b$c" ## otherwise copy as is
fi
i=$(expr $i + 1)
done
echo "output: $b" ## output resluting string
The case change is affected by relying on a simple bit-toggle of the case-bit (bit-6) in the ASCII value of each upper or lower case character to change it from lower to upper or vice-versa. (and note, you can exchange the printf and bit-shift for tr of asciic as an alternative)
Example Use/Output
$ sh togglecase.sh
input : This Is My 10TH String
output: tHIS iS mY 10th sTRING
When you want to swab every second characters case, try this:
read -p " Enter string " str
for i in `seq 0 ${#str}`; do
rem=$(($i % 2 ))
if [ $rem -eq 0 ]
then
printf "%s" "${str:$i:1}"
else
fr=${str:$i:1}
printf "%s" "$(tr '[:upper:][:lower:]' '[:lower:][:upper:]' <<< "${str:$i:1}")"
fi
done
echo
EDIT: Second solution
Switch case of str and merge the old and new string.
#!/bin/bash
str="part is lowercase & PART IS UPPERCASE"
str2=$(tr '[:upper:][:lower:]' '[:lower:][:upper:]' <<< "${str}")
str_chopped=$(sed -r 's/(.)./\1\n/g' <<< "${str}");
# Will have 1 additional char for odd length str
# str2_chopped_incorrect=$(sed -r 's/.(.)/\1\n/g' <<< "${str2}");
str2_chopped=$(fold -w2 <<< "${str2}" | sed -nr 's/.(.)/\1/p' );
paste -d '\n' <(echo "${str_chopped}") <(echo "${str2_chopped}") | tr -d '\n'; echo
My mate asked this before on the unix SE, but he asked it wrong. He didn't get a working answer either.
Anyway, I'm trying to make my bash script process each character in a variable and echo a certain string per letter until it reaches the last. Here's what I have so far:
#!/bin/bash
echo Word?
read -r -p '' foo
# $foo is set to 'Mammals and Bricks' by user.
wordlength=${#foo}
$wordlength says 18, so start on character 1.
'M' is first letter received in $foo, so echo '{m,M}'
'a' is second letter received in $foo, so echo '{a,A}'
'm' is third letter received in $foo, so echo '{m,M}'
'm' is fourth letter received in $foo, so echo '{m,M}'
'a' is the fifth letter received in $foo, so echo '{a,A}'
'l' is the sixth letter received in $foo, so echo '{l,L}'
's' is the seventh letter received in foo, so echo '{s,S}'
' ' is the eighth, so echo '\ '
........
'c' is sixteenth letter received in $foo, so echo '{c,C}'
'k' is seventeenth letter received in $foo, so echo '{k,K}'
's' is eighteenth letter received in $foo, so echo '{s,S}'
And here's what it would look like on the user's end:
Word?
Mammals and Bricks
{m,M}{a,A}{m,M}{m,M}{a,A}{l,L}{s,S} {a,A}{n,N}{d,D} {b,B}{r,R}{i,I}{c,C}{k,K}{s,S}
Which is what it would output exactly. You would see all of the above in raw characters.
Anyone know how to do this?
Below is a solution with GNU sed, if you don't mind using it:
sed 's/[a-zA-Z]/{\l&,\u&}/g' <<< "$foo"
\l and \u are GNU extensions to sed that turn the next character to lowercase and uppercase, respectively.
[edit] And here is a solution with bash since you haven't GNU sed:
while read -r -n1; do
if [[ "${REPLY^}" == [A-Z] ]]; then
printf '{%c,%c}' "${REPLY,}" "${REPLY^}"
else
printf '%c' "$REPLY"
fi
done <<< "$foo"
echo
[edit] P.S. Unfortunately, this won't work on OS X Yosemite as the ${var,} and ${var^} constructs were added in bash v4, but MacOS only ships with bash v3.2.57 (this is because bash v4 is licensed under GPL v3, which Apple doesn't want to comply with). Thanks to #GordonDavisson for adding this.
So here is a solution that should work with your bash v3:
printf '%s\n' "$foo" \
| while read -d '' -r -n1; do
lowercase="$(printf '%c' "$REPLY" | tr '[:upper:]' '[:lower:]')"
uppercase="$(printf '%c' "$REPLY" | tr '[:lower:]' '[:upper:]')"
if [ "$lowercase" != "$uppercase" ]; then
printf '{%c,%c}' "$lowercase" "$uppercase"
else
printf '%c' "$REPLY"
fi
done
Start by looping through the characters in your string:
foo=string
for (( i=0; i<${#foo}; i++ )); do
echo "${foo:$i:1}"
done
( Reference: How to perform a for loop on each character in a string in BASH? )
Now replace the echo statement with a case statement:
foo=string
for (( i=0; i<${#foo}; i++ )); do
case "${foo:$i:1}" in
a)
echo "Do something with a here";
;;
[bB])
echo "Do something with b or B here";
;;
esac
done
I am trying to the url encode a string based on shell scripting.
I have downloaded a script from internet.
it is:
#!/bin/sh
url_encoder()
{
echo -n "$1" | awk -v ORS="" '{ gsub(/./,"&\n") ; print }' | while read l;
do
case "$l" in
[-_.~/a-zA-Z0-9] ) echo -n ${l} ;;
"" ) echo -n %20 ;;
* ) printf '%%%02X' "'$l"
esac
done
}
echo ""
}
The basic idea of the above codes is to
(1) convert a input string into the rows, each row has one character
(2) for each row, url encode the character
So If I run
$url_encoder "abc:"
the output would be "abc%3A", which is correct
But if I run
$url_encoder "\\" # I want to encode the backslash, so I use 2 "\" here
there is no output at all.
Do you know the reason why?
no need to use read which is slow, variable expansion can do a substring, no need to handle the space character specially, it can be handled as the default
url_encoder() {
local i str=$1 c
for ((i=0;i<${#str};i+=1)); do
c=${str:i:1}
case "$c" in
[-_.~/a-zA-Z0-9] ) echo -n "${c}" ;;
* ) printf '%%%02X' "'$c" ;;
esac
done
}
l='\'
printf '%%%02X' "'$l"
The reason why the backslash disapears is because it has a special meaning for read, -r option should be used to avoid.
https://www.gnu.org/software/bash/manual/html_node/Bash-Builtins.html#index-read
Note ~ should also be encoded http://www.rfc-editor.org/rfc/rfc1738.txt
printf argument starting with a quote (single or double), handles only ascii character "'$c" (<128).
url_encoder() { (
LC_ALL=C
str=$1
for ((i=0;i<${#str};i+=1)); do
c=${str:i:1}
if [[ $c = [-_./a-zA-Z0-9] ]]; then
echo -n "${c}"
elif [[ $c = [$'\1'-$'\x7f'] ]]; then
printf '%%%02X' "'$c"
else
printf '%%%s' $(echo -n "$c" | od -An -tx1)
fi
done
)}
Nahuel Fouilleul's helpful answer explains the problem with your approach (-r is missing from your read command, resulting in unwanted interpretation of \ chars.) and offers a more efficient bash solution.
Here's a more efficient, POSIX-compliant solution (sh-compatible) that performs the encoding with a single awk command, assuming that the input string is composed only of characters in the ASCII/Unicode code-point range between 32 and 127, inclusively:
#!/bin/sh
url_encoder()
{
awk -v url="$1" -v ORS= 'BEGIN {
# Create lookup table that maps characters to their code points.
for(n=32;n<=127;n++) ord[sprintf("%c",n)]=n
# Process characters one by one, either passing them through, if they
# need no encoding, or converting them to their %-prefixed hex equivalent.
for(i=1;i<=length(url);++i) {
char = substr(url, i, 1)
if (char !~ "[-_.~/a-zA-Z0-9]") char = sprintf("%%%x", ord[char])
print char
}
printf "\n"
}'
}
is there some way to put variable in ALPHABETICAL range of cycle?
This doesnt work.
read -p "Where I should start?" start #there will be entered one small letter
for aaa in {$start..z}; do #how put variable $start in range?
...
done
Thanks for reply.
Use eval to expand the variable:
$ s=t
$ eval echo {$s..z}
t u v w x y z
Your example then becomes:
read -p "Where I should start?" start #there will be entered one small letter
for aaa in $(eval echo {$start..z}); do
echo $aaa
done
Since you have user input to eval, you may want to check the value of start as being a single lower case character first:
read -p "Where I should start?" start #there will be entered one small letter
if [[ $start =~ ^[a-y]$ ]]; then
for aaa in $(eval echo {$start..z}); do
echo $aaa
done
else
echo "Need to use a letter 'a-y'"
fi
You can read more about Bash brace expansion here
Unfortunately, you can't put variables inside {start..end} ranges in bash.
This does what you want:
until [[ $s == "_" ]]; do echo $s && s=$(tr "a-z" "b-z_" <<<$s); done
It uses tr to translate each character to the next one. "_" is the character after "z".
For example:
$ s=t
$ until [[ $s == "_" ]]; do echo $s && s=$(tr "a-z" "b-z_" <<<$s); done
t
u
v
w
x
y
z
If you don't mind using Perl, you could use this:
perl -le 'print for shift .. "z"' $s
It uses .. to create a list between the first argument on the command line and "z".
A slightly more esoteric way to do it in bash would be:
for ((i=$(LC_CTYPE=C printf '%d' "'$s"); i<=122; ++i)); do
printf "\\$(printf '%03o' $i)\n"
done
The for loop goes from the ASCII character number of the variable $s to "z", which is ASCII character 122. The format specifier the inner printf converts the character number to octal, padding it with zeros up to three characters long. The outer printf then interprets this as an escape sequence and prints the character. Credit goes to Greg's wiki for the code used to convert ASCII characters to their values.
Of course you could just use eval to expand the variable, the advantage being that the code required to do so is much shorter. However, executing arbitrary strings that have been read in to your script is arguably a bit of a security hole.
x=t
for I in $(sed -nr "s/.*($x.*)/\1/;s/ /\n/g;p" <(echo {a..z}))
do
# do something with $I
done
Output:
t
u
v
w
x
y
z
I would avoid the use of eval.
for aaa in {a..z}; do
[[ $aaa < $start ]] && continue
...
done
The overhead of comparing $aaa to $start should be negligible, especially compare to the cost of starting a separate process to compute the range.