I am using awk to split a string into array using a specific delimiter. Now, I want to perform some operation on each element of the array.
I am able to extract a single element like this:
#! /bin/bash
b=12:34:56
a=`echo $b | awk '{split($0,numbers,":"); print numbers[1]}'`
echo $a
I want to do something like this:
#! /bin/bash
b=12:34:56
`echo $b | awk '{split($0,numbers,":");}'`
for(i=0;i<length(numbers);i++)
{
// perform some operation using numbers[i]
}
how would I do something like this in bash scripting?
None of these answers used awk (weird). With awk you can do something like:
echo 12:34:56 | awk '{split($0,numbers,":")} END {for(n in numbers){ print numbers[n] }}'
replacing print numbers[n] with whatever it is you want to do.
You don't really need awk for that, bash can do some string processing all by itself.
Try:
b=12:34:56
for element in ${b//:/ } ; do
echo $element
done
If you need a counter, it's pretty trivial to add that.
See How do I do string manipulations in bash? for more info on what you can do directly in bash.
b=12:34:56
IFS=:
set -- $b
for i; do echo $i; done
This does not contain bashisms but works with every sh.
The bash read command can split a string into an array by itself:
IFS=: read -a numbers <<< "$b"
To see that it worked:
echo "Hours: ${numbers[0]}"
echo "Minutes: ${numbers[1]}"
echo "Seconds: ${numbers[2]}"
for val in "${numbers[#]}"; do
seconds=$(( seconds * 60 + $val ))
done
Another neat way, not using awk, but build-in 'declare':
b=12:34:56
# USE IFS for splitting (and elements can have spaces in them)
IFS=":"
declare -a elements=( $b )
#show contents
for (( i=0 ; i < ${#elements[#]}; i++ )); do
echo "$i= ${elements[$i]}"
done
Related
With this I can callmyscrip.sh 100 and this will print 100 rows with the content generated by seq, but what's the best way to separate the content TEXT="xxx yyy ${this}" for readability with a variable?
#!/bin/bash
howmanytimes=$1
for this in $(seq -w ${howmanytimes}); do echo " /
-- ${this}
"; done
this instead would not work as $this isn't replaced:
#!/bin/bash
howmanytimes=$1
TEXT="THIS WOULD NOT WORK: ${this}"
for this in $(seq -w ${howmanytimes}); do echo ${TEXT} ; done
export $TEXT
seq(1) is nonstandard, inefficient and useless.
Check http://mywiki.wooledge.org/BashGuide/TestsAndConditionals#Conditional_Loops
With ksh:
#!/bin/ksh
txt='this should work with int: '
for i in {0..$1}; do
echo "$txt $i"
done
With bash:
#!/bin/bash
txt='this should work with int: '
for ((i=0; i<=$1; i++)) {
echo "$txt $i"
}
You can wrap your dynamic text in a bash function:
#!/bin/bash
get_content() {
echo "THIS WOULD WORK: $1"
}
how_many_times=$1
for i in $(seq -w ${how_many_times}); do
echo "$(get_content $i)"
done
If you just need to output the content, can simplify it like this:
#!/bin/bash
get_content() {
echo "THIS WOULD WORK: $1"
}
how_many_times=$1
for i in $(seq -w ${how_many_times}); do
get_content $i
done
Check your script with shellcheck. printf is a simple template language. I could see:
#!/bin/bash
howmanytimes=$1
text="THIS WOULD WORK: %s"
for this in $(seq -w "${howmanytimes}"); do
printf "$text" "$this"
done
You could use envsubst to replace environment, however in this case printf looks way clearer. Research quoting in shell.
#!/bin/bash
howmanytimes=$1
text='THIS WOULD WORK: ${THIS}'
for this in $(seq -w "${howmanytimes}"); do
THIS="$this" envsubst <<<"$text"
done
You can use printf directly, and skip the loop entirely:
#!/bin/bash
howmanytimes=$1
text="This WILL work: %s"
printf "${text}\n" $(seq -w ${howmanytimes})
Note that \n needs to be added to the format string, since printf doesn't add a newline automatically like echo does. If you want additional newlines (like in the example), you can add them as either \n or actual newlines, in either the format variable or where it's used in the printf argument. Also, if you want to include a literal backslash or percent sign in the string, double it (i.e. %% to print %, or \\ to print \).
BTW, since printf is a bash builtin, it's not subject to the normal argument list length limits, so this'll work even with very large numbers of numbers.
I found interesting way to split string using tr or IFS
https://linuxhandbook.com/bash-split-string/
#!/bin/bash
#
# Script to split a string based on the delimiter
my_string="One;Two;Three"
my_array=($(echo $my_string | tr ";" "\n"))
#Print the split string
for i in "${my_array[#]}"
do
echo $i
done
Output
One
Two
Three
Based on this code, would be be possible to put a number in front of the string by using Bash?
In Python, there is enumerate function to accomplish this.
number = ['One', 'Two', 'Three']
for i,j in enumerate(number, 1):
print(f'{i} - {j}')
Output
1 - One
2 - Two
3 - Three
I belive there should be similar tricks can be done in Bash Shell probably with awk or sed, but I just can't think the solution for now.
I think you can just add something like count=$(($count+1))
#!/bin/bash
#
# Script to split a string based on the delimiter
my_string="One;Two;Three"
my_array=($(echo $my_string | tr ";" "\n"))
#Print the split string
count=0
for i in "${my_array[#]}"
do
count=$(($count+1))
echo $count - $i
done
This is a slightly modified version of #anubhava's answer.
y_string="One;Two;Three"
IFS=';' read -ra my_array <<< "$my_string"
# ${!array_name[#]} returns the indices/keys of the array
for i in "${!my_array[#]}"
do
echo "$((i+1)) - ${my_array[i]}"
done
From the bash manual,
It is possible to obtain the keys (indices) of an array as well as the values. ${!name[#]} and ${!name[*]} expand to the indices assigned in array variable name.
I saw you posted a post earlier today, sorry I failed to upload the code but still hope this could help you
my_string="AA-BBB"
IFS='-' read -ra my_array <<< "$my_string"
len=${#my_array[#]}
for (( i=0; i<$len; i++ )); do
up=$(($i % 2))
#echo $up
if [ $up -eq 0 ]
then
echo ${my_array[i]} = '"Country name"'
elif [ $up -eq 1 ]
then
echo ${my_array[i]} = '"City name"'
fi
done
Here is a standard bash way of doing this:
my_string="One;Two;Three"
IFS=';' read -ra my_array <<< "$my_string"
# builds my_array='([0]="One" [1]="Two" [2]="Three")'
# loop through array and print index+1 with element
# ${#my_array[#]} is length of the array
for ((i=0; i<${#my_array[#]}; i++)); do
printf '%d: %s\n' $((i+1)) "${my_array[i]}"
done
1: One
2: Two
3: Three
Assuming there is an input:
1,2,C
We are trying to output it as
KEY=1, VAL1=2, VAL2=C
So far trying to modify from here:
Is there a way to create key-value pairs in Bash script?
for i in 1,2,C ; do KEY=${i%,*,*}; VAL1=${i#*,}; VAL2=${i#*,*,}; echo $KEY" XX "$VAL1 XX "$VAL2"; done
Output:
1 XX 2,c XX c
Not entirely sure what the pound ("#") and % here mean above, making the modification kinda hard.
Could any guru enlighten? Thanks.
I would generally prefer easier to read code, as bash can get ugly pretty fast.
Try this:
key_values.sh
#!/bin/bash
IFS=,
count=0
# $* is the expansion of all the params passed in, i.e. $1, $2, $3, ...
for i in $*; do
# '-eq' is checking for equality, i.e. is $count equal to zero.
if [ $count -eq 0 ]; then
echo -n "KEY=$i"
else
echo -n ", VAL${count}=$i"
fi
count=$(( $count + 1 ))
done
echo
Example
key_values.sh 1,2,ABC,123,DEF
Output
KEY=1, VAL1=2, VAL2=ABC, VAL3=123, VAL4=DEF
Expanding on anishsane's comment:
$ echo $1
1,2,3,4,5
$ IFS=, read -ra args <<<"$1" # read into an array
$ out="KEY=${args[0]}"
$ for ((i=1; i < ${#args[#]}; i++)); do out+=", VAL$i=${args[i]}"; done
$ echo "$out"
KEY=1, VAL1=2, VAL2=3, VAL3=4, VAL4=5
How do I get an associative array from a query string in Bash? - Attempt:
#!/usr/bin/env bash
# Querystring (implementation stolen from http://stackoverflow.com/q/3919755)
function populate_querystring_array ()
{
param="$1"
query_dict="$2"
#for i in "${array[#]}"; do IFS="=" ; set -- $i; query_dict[$1]=$2; done
for ((i=0; i<${#param[#]}; i+=2))
do
query_dict[${param[i]}]=${param[i+1]}
done
}
q0='email=foo#bar.com&password=dfsa54'
declare -A querydict
populate_querystring_array "$q0" "$querydict"
printf "$querydict[email]"
#!/usr/bin/env bash
q0='email=foo#bar.com&password=dfsa54'
declare -A querydict
while IFS== read key value
do
querydict["$key"]="$value"
done < <(echo "$q0" | sed 's/&/\n/g' )
printf "${querydict[email]}\n"
In the above, 's/&/\n/g' is a sed command that replaces every occurrence of & with a new line. We apply this to q0 so that every parameter assignment is on a separate line. The parameter assignments are then read into the while loop. To read each assignment, IFS== read key value is used. IFS== tells read to treat the equal sign as a word separator. Thus, each assignment is broken into two words: the first is the key and the second is the value. These are then assigned to the associative array querydict with the statement querydict["$key"]="$value".
Putting it in a function
bash differs from most modern programming languages in that its facilities for passing complex data into and out of functions are extremely limited. In the method shown below, the associative array, querydict, is a global variable:
#!/usr/bin/env bash
declare -A querydict
populate_querystring_array () {
query="$1"
while IFS== read arg value
do
querydict["$arg"]="$value"
done < <(echo "$query" | sed 's/&/\n/g' )
}
q0='email=foo#bar.com&password=dfsa54'
populate_querystring_array "$q0"
printf "${querydict[email]}\n"
Below should work:
#!/bin/bash
function qrystring() {
qry=$1
while read key value; do
arr+=(["$key"]="$value")
done < <(awk -F'&' '{for(i=1;i<=NF;i++) {print $i}}' <<< $qry | awk -F'=' '{print $1" "$2}')
}
q='email=foo#bar.com&password=dfsa54'
declare -A arr
qrystring "$q"
for k in ${!arr[#]}; do
echo "$k -> ${arr[$k]}"
done
Explanation:
Im using a combination of awk commands to split the string into individual records first, then split on the = sign for kv pair.
I'm using process substitution here otherwise i would be populating a copy of the array.
EDIT:
Using a global variable to house array.
Taking #John1024's answer I use it in a function which returns the associative array by value, simply printing out the contents using array syntax:
function parseQuery {
local querystring="$*"
echo -n "("
echo "${querystring}" | sed 's/&/\n/g' | while IFS== read arg value
do
echo -n "[${arg}]='${value}' "
done
echo ")"
}
declare -A querydict=$(parseQuery "${QUERY_STRING}" )
In my script I need to expand an interval, e.g.:
input: 1,5-7
to get something like the following:
output: 1,5,6,7
I've found other solutions here, but they involve python and I can't use it in my script.
Solution with Just Bash 4 Builtins
You can use Bash range expansions. For example, assuming you've already parsed your input you can perform a series of successive operations to transform your range into a comma-separated series. For example:
value1=1
value2='5-7'
value2=${value2/-/..}
value2=`eval echo {$value2}`
echo "input: $value1,${value2// /,}"
All the usual caveats about the dangers of eval apply, and you'd definitely be better off solving this problem in Perl, Ruby, Python, or AWK. If you can't or won't, then you should at least consider including some pipeline tools like tr or sed in your conversions to avoid the need for eval.
Try something like this:
#!/bin/bash
for f in ${1//,/ }; do
if [[ $f =~ - ]]; then
a+=( $(seq ${f%-*} 1 ${f#*-}) )
else
a+=( $f )
fi
done
a=${a[*]}
a=${a// /,}
echo $a
Edit: As #Maxim_united mentioned in the comments, appending might be preferable to re-creating the array over and over again.
This should work with multiple ranges too.
#! /bin/bash
input="1,5-7,13-18,22"
result_str=""
for num in $(tr ',' ' ' <<< "$input"); do
if [[ "$num" == *-* ]]; then
res=$(seq -s ',' $(sed -n 's#\([0-9]\+\)-\([0-9]\+\).*#\1 \2#p' <<< "$num"))
else
res="$num"
fi
result_str="$result_str,$res"
done
echo ${result_str:1}
Will produce the following output:
1,5,6,7,13,14,15,16,17,18,22
expand_commas()
{
local arg
local st en i
set -- ${1//,/ }
for arg
do
case $arg in
[0-9]*-[0-9]*)
st=${arg%-*}
en=${arg#*-}
for ((i = st; i <= en; i++))
do
echo $i
done
;;
*)
echo $arg
;;
esac
done
}
Usage:
result=$(expand_commas arg)
eg:
result=$(expand_commas 1,5-7,9-12,3)
echo $result
You'll have to turn the separated words back into commas, of course.
It's a bit fragile with bad inputs but it's entirely in bash.
Here's my stab at it:
input=1,5-7,10,17-20
IFS=, read -a chunks <<< "$input"
output=()
for chunk in "${chunks[#]}"
do
IFS=- read -a args <<< "$chunk"
if (( ${#args[#]} == 1 )) # single number
then
output+=(${args[*]})
else # range
output+=($(seq "${args[#]}"))
fi
done
joined=$(sed -e 's/ /,/g' <<< "${output[*]}")
echo $joined
Basically split on commas, then interpret each piece. Then join back together with commas at the end.
A generic bash solution using the sequence expression `{x..y}'
#!/bin/bash
function doIt() {
local inp="${#/,/ }"
declare -a args=( $(echo ${inp/-/..}) )
local item
local sep
for item in "${args[#]}"
do
case ${item} in
*..*) eval "for i in {${item}} ; do echo -n \${sep}\${i}; sep=, ; done";;
*) echo -n ${sep}${item};;
esac
sep=,
done
}
doIt "1,5-7"
Should work with any input following the sample in the question. Also with multiple occurrences of x-y
Use only bash builtins
Using ideas from both #Ansgar Wiechers and #CodeGnome:
input="1,5-7,13-18,22"
for s in ${input//,/ }
do
if [[ $f =~ - ]]
then
a+=( $(eval echo {${s//-/..}}) )
else
a+=( $s )
fi
done
oldIFS=$IFS; IFS=$','; echo "${a[*]}"; IFS=$oldIFS
Works in Bash 3
Considering all the other answers, I came up with this solution, which does not use any sub-shells (but one call to eval for brace expansion) or separate processes:
# range list is assumed to be in $1 (e.g. 1-3,5,9-13)
# convert $1 to an array of ranges ("1-3" "5" "9-13")
IFS=,
local range=($1)
unset IFS
list=() # initialize result list
local r
for r in "${range[#]}"; do
if [[ $r == *-* ]]; then
# if the range is of the form "x-y",
# * convert to a brace expression "{x..y}",
# * using eval, this gets expanded to "x" "x+1" … "y" and
# * append this to the list array
eval list+=( {${r/-/..}} )
else
# otherwise, it is a simple number and can be appended to the array
list+=($r)
fi
done
# test output
echo ${list[#]}