I have two commas separate variables like below. on a certain condition, I need to merge two variables into a single. Bit confused and unsure if is it possible in bash
Input
SBI=abc,def,ijk
MEM=one,two,three
Expected output
OUT=abc_one,def_two,ijk_three
This is a simple extension of Iterate over two arrays simultaneously in bash, combined with How to split a string into an array in bash.
IFS=, read -ra sbi_arr <<<"$SBI" # convert SBI string to an array
IFS=, read -ra mem_arr <<<"$MEM" # convert MEM string to an array
out= # initialize output variable
for idx in "${!sbi_arr[#]}"; do # iterate by indices
out+="${sbi_arr[$idx]}_${mem_arr[$idx]}," # append to output
done
out=${out%,} # strip trailing comma from output
echo "Output is: $out"
Using bash command substitution, process substitution, parameter expansion and, paste utility:
OUT=$(paste -d_ <(echo "${SBI//,/$'\n'}") <(echo "${MEM//,/$'\n'}"))
OUT=${OUT//$'\n'/,}
echo "OUT=$OUT"
With sh.
#!/bin/sh
SBI=abc,def,ijk
MEM=one,two,three
out=$(
while [ -n "$SBI" ] && [ -n "$MEM" ]; do
sbi_first="${SBI%%,*}"
sbi_rest="${SBI#*"$sbi_first"}"
mem_first="${MEM%%,*}"
mem_rest="${MEM#*"$mem_first"}"
SBI="${sbi_rest#,}"
MEM="${mem_rest#,}"
printf '%s_%s,' "$sbi_first" "$mem_first"
done
)
echo "${out%,}"
With bash
#!/usr/bin/env bash
SBI=abc,def,ijk
MEM=one,two,three
while IFS= read -ru3 str0; do
IFS= read -r str1
out+="${str0}_$str1,"
done 3<<< "${SBI//,/$'\n'}" <<<"${MEM//,/$'\n'}"
echo "${out%,}"
I have a shell script, which gets bunch of values. I am segregating it based on a Delimiter(,). Now i want to print it one by one inside a for loop.
For E.g
var=/a/b/c,d/e/f/,x/y/z
for i in $(echo $var | sed "s/,/ /g")
do
echo $i
done
Output is coming empty, Expected output is
/a/b/c
d/e/f/
x/y/z
You don't need a loop.
sed 's/,/\n/g' <<< "$var"
sed 'y/,/\n/' <<< "$var"
tr ',' '\n' <<< "$var"
echo "${var//,/$'\n'}"
they all yield the desired output.
You could read it into an array. This is quite readable:
var=/a/b/c,d/e/f/,x/y/z
IFS=, read -a paths <<<"$var"
for p in "${paths[#]}"; do echo "$p"; done
/a/b/c
d/e/f/
x/y/z
Just to add another option -
var="/a/b/c,d/e/f/,x/y/z"
while IFS=, read a b c
do printf "a=$a b=$b c=$c\n"
done <<< "$var"
a=/a/b/c b=d/e/f/ c=x/y/z
Doesn't need a loop - works fine as
$: IFS=, read a b c <<< "$var"
$: printf "a=$a b=$b c=$c\n"
a=/a/b/c b=d/e/f/ c=x/y/z
... just wanted to show the loop structure in case it helped.
I have string like
name1::1.1.1.1::ps -ax
I want to split the string based on delimiter :: using bash scripting.
The desired output should be an array of 3 elements
("name1" "1.1.1.1" "ps -ax")
without double quotes
I appreciate your help.
Assuming there are no :s in the array data, use bash pattern substitution to squeeze the :: to : while assigning the string to $array, then show the whole array, then just element #2:
a="name1::1.1.1.1::ps -ax"
IFS=: array=(${a//::/:}) ; echo ${array[#]} ; echo "${array[2]}"
Output:
name1 1.1.1.1 ps -ax
ps -ax
But what if there are :s in the array data? Specifically in the third field, (the command), and only in that field. Use read with dummy variables to absorb the extra :: separators:
a="name1::1.1.1.1::parallel echo ::: 1 2 3 ::: a b"
IFS=: read x a y b z <<< "$a"; array=("$x" "$y" "$z"); printf "%s\n" "${array[#]}"
Output:
name1
1.1.1.1
parallel echo ::: 1 2 3 ::: a b
The only safe possibility is use a loop:
a='name1::1.1.1.1::ps -ax'
array=()
a+=:: # artificially append the separator
while [[ $a ]]; do
array+=( "${a%%::*}" )
a=${a#*::}
done
This will work with any symbol in a (spaces, glob characters, newlines, etc.)
echo "name1::1.1.1.1::ps -ax" | awk -F"::" '{print $1 $2 $3}'
i=0
string="name1::1.1.1.1::ps -ax"
echo "$string" | awk 'BEGIN{FS="::";OFS="\n"}{$1=$1;print $0}'>tempFile
while read line;
do
arr["$i"]="$line"
i=$(expr $i + 1)
done<tempFile
echo "${arr[#]}"
echo "${arr[0]}"
echo "${arr[1]}"
echo "${arr[2]}"
Output:
sh-4.4$ ./script1.sh
name1 1.1.1.1 ps -ax
name1
1.1.1.1
ps -ax
I'm new to bash scripting, I'm learning how commands work, I stumble in this problem,
I have a file /home/fedora/file.txt
Inside of the file is like this:
[apple] This is a fruit.
[ball] This is a sport's equipment.
[cat] This is an animal.
What I wanted is to retrieve words between "[" and "]".
What I tried so far is :
while IFS='' read -r line || [[ -n "$line" ]];
do
echo $line | awk -F"[" '{print$2}' | awk -F"]" '{print$1}'
done < /home/fedora/file.txt
I can print the words between "[" and "]".
Then I wanted to put the echoed word into a variable but i don't know how to.
Any help I will appreciate.
Try this:
variable="$(echo $line | awk -F"[" '{print$2}' | awk -F"]" '{print$1}')"
or
variable="$(awk -F'[\[\]]' '{print $2}' <<< "$line")"
or complete
while IFS='[]' read -r foo fruit rest; do echo $fruit; done < file
or with an array:
while IFS='[]' read -ra var; do echo "${var[1]}"; done < file
In addition to using awk, you can use the native parameter expansion/substring extraction provided by bash. Below # indicates a trim from the left, while % is used to trim from the right. (note: a single # or % indicates removal up to the first occurrence, while ## or %% indicates removal of all occurrences):
#!/bin/bash
[ -r "$1" ] || { ## validate input is readable
printf "error: insufficient input. usage: %s filename\n" "${0##*/}"
exit 1
}
## read each line and separate label and value
while read -r line || [ -n "$line" ]; do
label=${line#[} # trim initial [ from left
label=${label%%]*} # trim through ] from right
value=${line##*] } # trim from left through '[ '
printf " %-8s -> '%s'\n" "$label" "$value"
done <"$1"
exit 0
Input
$ cat dat/labels.txt
[apple] This is a fruit.
[ball] This is a sport's equipment.
[cat] This is an animal.
Output
$ bash readlabel.sh dat/labels.txt
apple -> 'This is a fruit.'
ball -> 'This is a sport's equipment.'
cat -> 'This is an animal.'
I have a string in a Bash shell script that I want to split into an array of characters, not based on a delimiter but just one character per array index. How can I do this? Ideally it would not use any external programs. Let me rephrase that. My goal is portability, so things like sed that are likely to be on any POSIX compatible system are fine.
Try
echo "abcdefg" | fold -w1
Edit: Added a more elegant solution suggested in comments.
echo "abcdefg" | grep -o .
You can access each letter individually already without an array conversion:
$ foo="bar"
$ echo ${foo:0:1}
b
$ echo ${foo:1:1}
a
$ echo ${foo:2:1}
r
If that's not enough, you could use something like this:
$ bar=($(echo $foo|sed 's/\(.\)/\1 /g'))
$ echo ${bar[1]}
a
If you can't even use sed or something like that, you can use the first technique above combined with a while loop using the original string's length (${#foo}) to build the array.
Warning: the code below does not work if the string contains whitespace. I think Vaughn Cato's answer has a better chance at surviving with special chars.
thing=($(i=0; while [ $i -lt ${#foo} ] ; do echo ${foo:$i:1} ; i=$((i+1)) ; done))
As an alternative to iterating over 0 .. ${#string}-1 with a for/while loop, there are two other ways I can think of to do this with only bash: using =~ and using printf. (There's a third possibility using eval and a {..} sequence expression, but this lacks clarity.)
With the correct environment and NLS enabled in bash these will work with non-ASCII as hoped, removing potential sources of failure with older system tools such as sed, if that's a concern. These will work from bash-3.0 (released 2005).
Using =~ and regular expressions, converting a string to an array in a single expression:
string="wonkabars"
[[ "$string" =~ ${string//?/(.)} ]] # splits into array
printf "%s\n" "${BASH_REMATCH[#]:1}" # loop free: reuse fmtstr
declare -a arr=( "${BASH_REMATCH[#]:1}" ) # copy array for later
The way this works is to perform an expansion of string which substitutes each single character for (.), then match this generated regular expression with grouping to capture each individual character into BASH_REMATCH[]. Index 0 is set to the entire string, since that special array is read-only you cannot remove it, note the :1 when the array is expanded to skip over index 0, if needed.
Some quick testing for non-trivial strings (>64 chars) shows this method is substantially faster than one using bash string and array operations.
The above will work with strings containing newlines, =~ supports POSIX ERE where . matches anything except NUL by default, i.e. the regex is compiled without REG_NEWLINE. (The behaviour of POSIX text processing utilities is allowed to be different by default in this respect, and usually is.)
Second option, using printf:
string="wonkabars"
ii=0
while printf "%s%n" "${string:ii++:1}" xx; do
((xx)) && printf "\n" || break
done
This loop increments index ii to print one character at a time, and breaks out when there are no characters left. This would be even simpler if the bash printf returned the number of character printed (as in C) rather than an error status, instead the number of characters printed is captured in xx using %n. (This works at least back as far as bash-2.05b.)
With bash-3.1 and printf -v var you have slightly more flexibility, and can avoid falling off the end of the string should you be doing something other than printing the characters, e.g. to create an array:
declare -a arr
ii=0
while printf -v cc "%s%n" "${string:(ii++):1}" xx; do
((xx)) && arr+=("$cc") || break
done
If your string is stored in variable x, this produces an array y with the individual characters:
i=0
while [ $i -lt ${#x} ]; do y[$i]=${x:$i:1}; i=$((i+1));done
The most simple, complete and elegant solution:
$ read -a ARRAY <<< $(echo "abcdefg" | sed 's/./& /g')
and test
$ echo ${ARRAY[0]}
a
$ echo ${ARRAY[1]}
b
Explanation: read -a reads the stdin as an array and assigns it to the variable ARRAY treating spaces as delimiter for each array item.
The evaluation of echoing the string to sed just add needed spaces between each character.
We are using Here String (<<<) to feed the stdin of the read command.
I have found that the following works the best:
array=( `echo string | grep -o . ` )
(note the backticks)
then if you do: echo ${array[#]} ,
you get: s t r i n g
or: echo ${array[2]} ,
you get: r
Pure Bash solution with no loop:
#!/usr/bin/env bash
str='The quick brown fox jumps over a lazy dog.'
# Need extglob for the replacement pattern
shopt -s extglob
# Split string characters into array (skip first record)
# Character 037 is the octal representation of ASCII Record Separator
# so it can capture all other characters in the string, including spaces.
IFS= mapfile -s1 -t -d $'\37' array <<<"${str//?()/$'\37'}"
# Strip out captured trailing newline of here-string in last record
array[-1]="${array[-1]%?}"
# Debug print array
declare -p array
string=hello123
for i in $(seq 0 ${#string})
do array[$i]=${string:$i:1}
done
echo "zero element of array is [${array[0]}]"
echo "entire array is [${array[#]}]"
The zero element of array is [h]. The entire array is [h e l l o 1 2 3 ].
Yet another on :), the stated question simply says 'Split string into character array' and don't say much about the state of the receiving array, and don't say much about special chars like and control chars.
My assumption is that if I want to split a string into an array of chars I want the receiving array containing just that string and no left over from previous runs, yet preserve any special chars.
For instance the proposed solution family like
for (( i=0 ; i < ${#x} ; i++ )); do y[i]=${x:i:1}; done
Have left overs in the target array.
$ y=(1 2 3 4 5 6 7 8)
$ x=abc
$ for (( i=0 ; i < ${#x} ; i++ )); do y[i]=${x:i:1}; done
$ printf '%s ' "${y[#]}"
a b c 4 5 6 7 8
Beside writing the long line each time we want to split a problem, so why not hide all this into a function we can keep is a package source file, with a API like
s2a "Long string" ArrayName
I got this one that seems to do the job.
$ s2a()
> { [ "$2" ] && typeset -n __=$2 && unset $2;
> [ "$1" ] && __+=("${1:0:1}") && s2a "${1:1}"
> }
$ a=(1 2 3 4 5 6 7 8 9 0) ; printf '%s ' "${a[#]}"
1 2 3 4 5 6 7 8 9 0
$ s2a "Split It" a ; printf '%s ' "${a[#]}"
S p l i t I t
If the text can contain spaces:
eval a=( $(echo "this is a test" | sed "s/\(.\)/'\1' /g") )
$ echo hello | awk NF=NF FS=
h e l l o
Or
$ echo hello | awk '$0=RT' RS=[[:alnum:]]
h
e
l
l
o
I know this is a "bash" question, but please let me show you the perfect solution in zsh, a shell very popular these days:
string='this is a string'
string_array=(${(s::)string}) #Parameter expansion. And that's it!
print ${(t)string_array} -> type array
print $#string_array -> 16 items
This is an old post/thread but with a new feature of bash v5.2+ using the shell option patsub_replacement and the =~ operator for regex. More or less same with #mr.spuratic post/answer.
str='There can be only one, the Highlander.'
regexp="${str//?/(&)}"
[[ "$str" =~ $regexp ]] &&
printf '%s\n' "${BASH_REMATCH[#]:1}"
Or by just: (which includes the whole string at index 0)
declare -p BASH_REMATCH
If that is not desired, one can remove the value of the first index (index 0), with
unset -v 'BASH_REMATCH[0]'
instead of using printf or echo to print the value of the array BASH_REMATCH
One can check/see the value of the variable "$regexp" with either
declare -p regexp
Output
declare -- regexp="(T)(h)(e)(r)(e)( )(c)(a)(n)( )(b)(e)( )(o)(n)(l)(y)( )(o)(n)(e)(,)( )(t)(h)(e)( )(H)(i)(g)(h)(l)(a)(n)(d)(e)(r)(.)"
or
echo "$regexp"
Using it in a script, one might want to test if the shopt is enabled or not, although the manual says it is on/enabled by default.
Something like.
if ! shopt -q patsub_replacement; then
shopt -s patsub_replacement
fi
But yeah, check the bash version too! If you're not sure which version of bash is in use.
if ! ((BASH_VERSINFO[0] >= 5 && BASH_VERSINFO[1] >= 2)); then
printf 'No dice! bash version 5.2+ is required!\n' >&2
exit 1
fi
Space can be excluded from regexp variable, change it from
regexp="${str//?/(&)}"
To
regexp="${str//[! ]/(&)}"
and the output is:
declare -- regexp="(T)(h)(e)(r)(e) (c)(a)(n) (b)(e) (o)(n)(l)(y) (o)(n)(e) (t)(h)(e) (H)(i)(g)(h)(l)(a)(n)(d)(e)(r)(.)"
Maybe not as efficient as the other post/answer but it is still a solution/option.
If you want to store this in an array, you can do this:
string=foo
unset chars
declare -a chars
while read -N 1
do
chars[${#chars[#]}]="$REPLY"
done <<<"$string"x
unset chars[$((${#chars[#]} - 1))]
unset chars[$((${#chars[#]} - 1))]
echo "Array: ${chars[#]}"
Array: f o o
echo "Array length: ${#chars[#]}"
Array length: 3
The final x is necessary to handle the fact that a newline is appended after $string if it doesn't contain one.
If you want to use NUL-separated characters, you can try this:
echo -n "$string" | while read -N 1
do
printf %s "$REPLY"
printf '\0'
done
AWK is quite convenient:
a='123'; echo $a | awk 'BEGIN{FS="";OFS=" "} {print $1,$2,$3}'
where FS and OFS is delimiter for read-in and print-out
For those who landed here searching how to do this in fish:
We can use the builtin string command (since v2.3.0) for string manipulation.
↪ string split '' abc
a
b
c
The output is a list, so array operations will work.
↪ for c in (string split '' abc)
echo char is $c
end
char is a
char is b
char is c
Here's a more complex example iterating over the string with an index.
↪ set --local chars (string split '' abc)
for i in (seq (count $chars))
echo $i: $chars[$i]
end
1: a
2: b
3: c
zsh solution: To put the scalar string variable into arr, which will be an array:
arr=(${(ps::)string})
If you also need support for strings with newlines, you can do:
str2arr(){ local string="$1"; mapfile -d $'\0' Chars < <(for i in $(seq 0 $((${#string}-1))); do printf '%s\u0000' "${string:$i:1}"; done); printf '%s' "(${Chars[*]#Q})" ;}
string=$(printf '%b' "apa\nbepa")
declare -a MyString=$(str2arr "$string")
declare -p MyString
# prints declare -a MyString=([0]="a" [1]="p" [2]="a" [3]=$'\n' [4]="b" [5]="e" [6]="p" [7]="a")
As a response to Alexandro de Oliveira, I think the following is more elegant or at least more intuitive:
while read -r -n1 c ; do arr+=("$c") ; done <<<"hejsan"
declare -r some_string='abcdefghijklmnopqrstuvwxyz'
declare -a some_array
declare -i idx
for ((idx = 0; idx < ${#some_string}; ++idx)); do
some_array+=("${some_string:idx:1}")
done
for idx in "${!some_array[#]}"; do
echo "$((idx)): ${some_array[idx]}"
done
Pure bash, no loop.
Another solution, similar to/adapted from Léa Gris' solution, but using read -a instead of readarray/mapfile :
#!/usr/bin/env bash
str='azerty'
# Need extglob for the replacement pattern
shopt -s extglob
# Split string characters into array
# ${str//?()/$'\x1F'} replace each character "c" with "^_c".
# ^_ (Control-_, 0x1f) is Unit Separator (US), you can choose another
# character.
IFS=$'\x1F' read -ra array <<< "${str//?()/$'\x1F'}"
# now, array[0] contains an empty string and the rest of array (starting
# from index 1) contains the original string characters :
declare -p array
# Or, if you prefer to keep the array "clean", you can delete
# the first element and pack the array :
unset array[0]
array=("${array[#]}")
declare -p array
However, I prefer the shorter (and easier to understand for me), where we remove the initial 0x1f before assigning the array :
#!/usr/bin/env bash
str='azerty'
shopt -s extglob
tmp="${str//?()/$'\x1F'}" # same as code above
tmp=${tmp#$'\x1F'} # remove initial 0x1f
IFS=$'\x1F' read -ra array <<< "$tmp" # assign array
declare -p array # verification