Related
I have this string stored in a variable:
IN="bla#some.com;john#home.com"
Now I would like to split the strings by ; delimiter so that I have:
ADDR1="bla#some.com"
ADDR2="john#home.com"
I don't necessarily need the ADDR1 and ADDR2 variables. If they are elements of an array that's even better.
After suggestions from the answers below, I ended up with the following which is what I was after:
#!/usr/bin/env bash
IN="bla#some.com;john#home.com"
mails=$(echo $IN | tr ";" "\n")
for addr in $mails
do
echo "> [$addr]"
done
Output:
> [bla#some.com]
> [john#home.com]
There was a solution involving setting Internal_field_separator (IFS) to ;. I am not sure what happened with that answer, how do you reset IFS back to default?
RE: IFS solution, I tried this and it works, I keep the old IFS and then restore it:
IN="bla#some.com;john#home.com"
OIFS=$IFS
IFS=';'
mails2=$IN
for x in $mails2
do
echo "> [$x]"
done
IFS=$OIFS
BTW, when I tried
mails2=($IN)
I only got the first string when printing it in loop, without brackets around $IN it works.
You can set the internal field separator (IFS) variable, and then let it parse into an array. When this happens in a command, then the assignment to IFS only takes place to that single command's environment (to read ). It then parses the input according to the IFS variable value into an array, which we can then iterate over.
This example will parse one line of items separated by ;, pushing it into an array:
IFS=';' read -ra ADDR <<< "$IN"
for i in "${ADDR[#]}"; do
# process "$i"
done
This other example is for processing the whole content of $IN, each time one line of input separated by ;:
while IFS=';' read -ra ADDR; do
for i in "${ADDR[#]}"; do
# process "$i"
done
done <<< "$IN"
Taken from Bash shell script split array:
IN="bla#some.com;john#home.com"
arrIN=(${IN//;/ })
echo ${arrIN[1]} # Output: john#home.com
Explanation:
This construction replaces all occurrences of ';' (the initial // means global replace) in the string IN with ' ' (a single space), then interprets the space-delimited string as an array (that's what the surrounding parentheses do).
The syntax used inside of the curly braces to replace each ';' character with a ' ' character is called Parameter Expansion.
There are some common gotchas:
If the original string has spaces, you will need to use IFS:
IFS=':'; arrIN=($IN); unset IFS;
If the original string has spaces and the delimiter is a new line, you can set IFS with:
IFS=$'\n'; arrIN=($IN); unset IFS;
I've seen a couple of answers referencing the cut command, but they've all been deleted. It's a little odd that nobody has elaborated on that, because I think it's one of the more useful commands for doing this type of thing, especially for parsing delimited log files.
In the case of splitting this specific example into a bash script array, tr is probably more efficient, but cut can be used, and is more effective if you want to pull specific fields from the middle.
Example:
$ echo "bla#some.com;john#home.com" | cut -d ";" -f 1
bla#some.com
$ echo "bla#some.com;john#home.com" | cut -d ";" -f 2
john#home.com
You can obviously put that into a loop, and iterate the -f parameter to pull each field independently.
This gets more useful when you have a delimited log file with rows like this:
2015-04-27|12345|some action|an attribute|meta data
cut is very handy to be able to cat this file and select a particular field for further processing.
If you don't mind processing them immediately, I like to do this:
for i in $(echo $IN | tr ";" "\n")
do
# process
done
You could use this kind of loop to initialize an array, but there's probably an easier way to do it.
Compatible answer
There are a lot of different ways to do this in bash.
However, it's important to first note that bash has many special features (so-called bashisms) that won't work in any other shell.
In particular, arrays, associative arrays, and pattern substitution, which are used in the solutions in this post as well as others in the thread, are bashisms and may not work under other shells that many people use.
For instance: on my Debian GNU/Linux, there is a standard shell called dash; I know many people who like to use another shell called ksh; and there is also a special tool called busybox with his own shell interpreter (ash).
For posix shell compatible answer, go to last part of this answer!
Requested string
The string to be split in the above question is:
IN="bla#some.com;john#home.com"
I will use a modified version of this string to ensure that my solution is robust to strings containing whitespace, which could break other solutions:
IN="bla#some.com;john#home.com;Full Name <fulnam#other.org>"
Split string based on delimiter in bash (version >=4.2)
In pure bash, we can create an array with elements split by a temporary value for IFS (the input field separator). The IFS, among other things, tells bash which character(s) it should treat as a delimiter between elements when defining an array:
IN="bla#some.com;john#home.com;Full Name <fulnam#other.org>"
# save original IFS value so we can restore it later
oIFS="$IFS"
IFS=";"
declare -a fields=($IN)
IFS="$oIFS"
unset oIFS
In newer versions of bash, prefixing a command with an IFS definition changes the IFS for that command only and resets it to the previous value immediately afterwards. This means we can do the above in just one line:
IFS=\; read -a fields <<<"$IN"
# after this command, the IFS resets back to its previous value (here, the default):
set | grep ^IFS=
# IFS=$' \t\n'
We can see that the string IN has been stored into an array named fields, split on the semicolons:
set | grep ^fields=\\\|^IN=
# fields=([0]="bla#some.com" [1]="john#home.com" [2]="Full Name <fulnam#other.org>")
# IN='bla#some.com;john#home.com;Full Name <fulnam#other.org>'
(We can also display the contents of these variables using declare -p:)
declare -p IN fields
# declare -- IN="bla#some.com;john#home.com;Full Name <fulnam#other.org>"
# declare -a fields=([0]="bla#some.com" [1]="john#home.com" [2]="Full Name <fulnam#other.org>")
Note that read is the quickest way to do the split because there are no forks or external resources called.
Once the array is defined, you can use a simple loop to process each field (or, rather, each element in the array you've now defined):
# `"${fields[#]}"` expands to return every element of `fields` array as a separate argument
for x in "${fields[#]}" ;do
echo "> [$x]"
done
# > [bla#some.com]
# > [john#home.com]
# > [Full Name <fulnam#other.org>]
Or you could drop each field from the array after processing using a shifting approach, which I like:
while [ "$fields" ] ;do
echo "> [$fields]"
# slice the array
fields=("${fields[#]:1}")
done
# > [bla#some.com]
# > [john#home.com]
# > [Full Name <fulnam#other.org>]
And if you just want a simple printout of the array, you don't even need to loop over it:
printf "> [%s]\n" "${fields[#]}"
# > [bla#some.com]
# > [john#home.com]
# > [Full Name <fulnam#other.org>]
Update: recent bash >= 4.4
In newer versions of bash, you can also play with the command mapfile:
mapfile -td \; fields < <(printf "%s\0" "$IN")
This syntax preserve special chars, newlines and empty fields!
If you don't want to include empty fields, you could do the following:
mapfile -td \; fields <<<"$IN"
fields=("${fields[#]%$'\n'}") # drop '\n' added by '<<<'
With mapfile, you can also skip declaring an array and implicitly "loop" over the delimited elements, calling a function on each:
myPubliMail() {
printf "Seq: %6d: Sending mail to '%s'..." $1 "$2"
# mail -s "This is not a spam..." "$2" </path/to/body
printf "\e[3D, done.\n"
}
mapfile < <(printf "%s\0" "$IN") -td \; -c 1 -C myPubliMail
(Note: the \0 at end of the format string is useless if you don't care about empty fields at end of the string or they're not present.)
mapfile < <(echo -n "$IN") -td \; -c 1 -C myPubliMail
# Seq: 0: Sending mail to 'bla#some.com', done.
# Seq: 1: Sending mail to 'john#home.com', done.
# Seq: 2: Sending mail to 'Full Name <fulnam#other.org>', done.
Or you could use <<<, and in the function body include some processing to drop the newline it adds:
myPubliMail() {
local seq=$1 dest="${2%$'\n'}"
printf "Seq: %6d: Sending mail to '%s'..." $seq "$dest"
# mail -s "This is not a spam..." "$dest" </path/to/body
printf "\e[3D, done.\n"
}
mapfile <<<"$IN" -td \; -c 1 -C myPubliMail
# Renders the same output:
# Seq: 0: Sending mail to 'bla#some.com', done.
# Seq: 1: Sending mail to 'john#home.com', done.
# Seq: 2: Sending mail to 'Full Name <fulnam#other.org>', done.
Split string based on delimiter in shell
If you can't use bash, or if you want to write something that can be used in many different shells, you often can't use bashisms -- and this includes the arrays we've been using in the solutions above.
However, we don't need to use arrays to loop over "elements" of a string. There is a syntax used in many shells for deleting substrings of a string from the first or last occurrence of a pattern. Note that * is a wildcard that stands for zero or more characters:
(The lack of this approach in any solution posted so far is the main reason I'm writing this answer ;)
${var#*SubStr} # drops substring from start of string up to first occurrence of `SubStr`
${var##*SubStr} # drops substring from start of string up to last occurrence of `SubStr`
${var%SubStr*} # drops substring from last occurrence of `SubStr` to end of string
${var%%SubStr*} # drops substring from first occurrence of `SubStr` to end of string
As explained by Score_Under:
# and % delete the shortest possible matching substring from the start and end of the string respectively, and
## and %% delete the longest possible matching substring.
Using the above syntax, we can create an approach where we extract substring "elements" from the string by deleting the substrings up to or after the delimiter.
The codeblock below works well in bash (including Mac OS's bash), dash, ksh, lksh, yash, zsh, and busybox's ash:
(Thanks to Adam Katz's comment, making this loop a lot simplier!)
IN="bla#some.com;john#home.com;Full Name <fulnam#other.org>"
while [ "$IN" != "$iter" ] ;do
# extract the substring from start of string up to delimiter.
iter=${IN%%;*}
# delete this first "element" AND next separator, from $IN.
IN="${IN#$iter;}"
# Print (or doing anything with) the first "element".
printf '> [%s]\n' "$iter"
done
# > [bla#some.com]
# > [john#home.com]
# > [Full Name <fulnam#other.org>]
Why not cut?
cut is usefull for extracting columns in big files, but doing forks repetitively (var=$(echo ... | cut ...)) become quickly overkill!
Here is a correct syntax, tested under many posix shell using cut, as suggested by This other answer from DougW:
IN="bla#some.com;john#home.com;Full Name <fulnam#other.org>"
i=1
while iter=$(echo "$IN"|cut -d\; -f$i) ; [ -n "$iter" ] ;do
printf '> [%s]\n' "$iter"
i=$((i+1))
done
I wrote this in order to compare execution time.
On my raspberrypi, this look like:
$ export TIMEFORMAT=$'(%U + %S) / \e[1m%R\e[0m : %P '
$ time sh splitDemo.sh >/dev/null
(0.000 + 0.019) / 0.019 : 99.63
$ time sh splitDemo_cut.sh >/dev/null
(0.051 + 0.041) / 0.188 : 48.98
Where overall execution time is something like 10x longer, using 1 forks to cut, by field!
This worked for me:
string="1;2"
echo $string | cut -d';' -f1 # output is 1
echo $string | cut -d';' -f2 # output is 2
I think AWK is the best and efficient command to resolve your problem. AWK is included by default in almost every Linux distribution.
echo "bla#some.com;john#home.com" | awk -F';' '{print $1,$2}'
will give
bla#some.com john#home.com
Of course your can store each email address by redefining the awk print field.
How about this approach:
IN="bla#some.com;john#home.com"
set -- "$IN"
IFS=";"; declare -a Array=($*)
echo "${Array[#]}"
echo "${Array[0]}"
echo "${Array[1]}"
Source
echo "bla#some.com;john#home.com" | sed -e 's/;/\n/g'
bla#some.com
john#home.com
This also works:
IN="bla#some.com;john#home.com"
echo ADD1=`echo $IN | cut -d \; -f 1`
echo ADD2=`echo $IN | cut -d \; -f 2`
Be careful, this solution is not always correct. In case you pass "bla#some.com" only, it will assign it to both ADD1 and ADD2.
A different take on Darron's answer, this is how I do it:
IN="bla#some.com;john#home.com"
read ADDR1 ADDR2 <<<$(IFS=";"; echo $IN)
How about this one liner, if you're not using arrays:
IFS=';' read ADDR1 ADDR2 <<<$IN
In Bash, a bullet proof way, that will work even if your variable contains newlines:
IFS=';' read -d '' -ra array < <(printf '%s;\0' "$in")
Look:
$ in=$'one;two three;*;there is\na newline\nin this field'
$ IFS=';' read -d '' -ra array < <(printf '%s;\0' "$in")
$ declare -p array
declare -a array='([0]="one" [1]="two three" [2]="*" [3]="there is
a newline
in this field")'
The trick for this to work is to use the -d option of read (delimiter) with an empty delimiter, so that read is forced to read everything it's fed. And we feed read with exactly the content of the variable in, with no trailing newline thanks to printf. Note that's we're also putting the delimiter in printf to ensure that the string passed to read has a trailing delimiter. Without it, read would trim potential trailing empty fields:
$ in='one;two;three;' # there's an empty field
$ IFS=';' read -d '' -ra array < <(printf '%s;\0' "$in")
$ declare -p array
declare -a array='([0]="one" [1]="two" [2]="three" [3]="")'
the trailing empty field is preserved.
Update for Bash≥4.4
Since Bash 4.4, the builtin mapfile (aka readarray) supports the -d option to specify a delimiter. Hence another canonical way is:
mapfile -d ';' -t array < <(printf '%s;' "$in")
Without setting the IFS
If you just have one colon you can do that:
a="foo:bar"
b=${a%:*}
c=${a##*:}
you will get:
b = foo
c = bar
Here is a clean 3-liner:
in="foo#bar;bizz#buzz;fizz#buzz;buzz#woof"
IFS=';' list=($in)
for item in "${list[#]}"; do echo $item; done
where IFS delimit words based on the separator and () is used to create an array. Then [#] is used to return each item as a separate word.
If you've any code after that, you also need to restore $IFS, e.g. unset IFS.
The following Bash/zsh function splits its first argument on the delimiter given by the second argument:
split() {
local string="$1"
local delimiter="$2"
if [ -n "$string" ]; then
local part
while read -d "$delimiter" part; do
echo $part
done <<< "$string"
echo $part
fi
}
For instance, the command
$ split 'a;b;c' ';'
yields
a
b
c
This output may, for instance, be piped to other commands. Example:
$ split 'a;b;c' ';' | cat -n
1 a
2 b
3 c
Compared to the other solutions given, this one has the following advantages:
IFS is not overriden: Due to dynamic scoping of even local variables, overriding IFS over a loop causes the new value to leak into function calls performed from within the loop.
Arrays are not used: Reading a string into an array using read requires the flag -a in Bash and -A in zsh.
If desired, the function may be put into a script as follows:
#!/usr/bin/env bash
split() {
# ...
}
split "$#"
you can apply awk to many situations
echo "bla#some.com;john#home.com"|awk -F';' '{printf "%s\n%s\n", $1, $2}'
also you can use this
echo "bla#some.com;john#home.com"|awk -F';' '{print $1,$2}' OFS="\n"
There is a simple and smart way like this:
echo "add:sfff" | xargs -d: -i echo {}
But you must use gnu xargs, BSD xargs cant support -d delim. If you use apple mac like me. You can install gnu xargs :
brew install findutils
then
echo "add:sfff" | gxargs -d: -i echo {}
So many answers and so many complexities. Try out a simpler solution:
echo "string1, string2" | tr , "\n"
tr (read, translate) replaces the first argument with the second argument in the input.
So tr , "\n" replace the comma with new line character in the input and it becomes:
string1
string2
There are some cool answers here (errator esp.), but for something analogous to split in other languages -- which is what I took the original question to mean -- I settled on this:
IN="bla#some.com;john#home.com"
declare -a a="(${IN//;/ })";
Now ${a[0]}, ${a[1]}, etc, are as you would expect. Use ${#a[*]} for number of terms. Or to iterate, of course:
for i in ${a[*]}; do echo $i; done
IMPORTANT NOTE:
This works in cases where there are no spaces to worry about, which solved my problem, but may not solve yours. Go with the $IFS solution(s) in that case.
If no space, Why not this?
IN="bla#some.com;john#home.com"
arr=(`echo $IN | tr ';' ' '`)
echo ${arr[0]}
echo ${arr[1]}
This is the simplest way to do it.
spo='one;two;three'
OIFS=$IFS
IFS=';'
spo_array=($spo)
IFS=$OIFS
echo ${spo_array[*]}
Apart from the fantastic answers that were already provided, if it is just a matter of printing out the data you may consider using awk:
awk -F";" '{for (i=1;i<=NF;i++) printf("> [%s]\n", $i)}' <<< "$IN"
This sets the field separator to ;, so that it can loop through the fields with a for loop and print accordingly.
Test
$ IN="bla#some.com;john#home.com"
$ awk -F";" '{for (i=1;i<=NF;i++) printf("> [%s]\n", $i)}' <<< "$IN"
> [bla#some.com]
> [john#home.com]
With another input:
$ awk -F";" '{for (i=1;i<=NF;i++) printf("> [%s]\n", $i)}' <<< "a;b;c d;e_;f"
> [a]
> [b]
> [c d]
> [e_]
> [f]
IN="bla#some.com;john#home.com"
IFS=';'
read -a IN_arr <<< "${IN}"
for entry in "${IN_arr[#]}"
do
echo $entry
done
Output
bla#some.com
john#home.com
System : Ubuntu 12.04.1
Use the set built-in to load up the $# array:
IN="bla#some.com;john#home.com"
IFS=';'; set $IN; IFS=$' \t\n'
Then, let the party begin:
echo $#
for a; do echo $a; done
ADDR1=$1 ADDR2=$2
Two bourne-ish alternatives where neither require bash arrays:
Case 1: Keep it nice and simple: Use a NewLine as the Record-Separator... eg.
IN="bla#some.com
john#home.com"
while read i; do
# process "$i" ... eg.
echo "[email:$i]"
done <<< "$IN"
Note: in this first case no sub-process is forked to assist with list manipulation.
Idea: Maybe it is worth using NL extensively internally, and only converting to a different RS when generating the final result externally.
Case 2: Using a ";" as a record separator... eg.
NL="
" IRS=";" ORS=";"
conv_IRS() {
exec tr "$1" "$NL"
}
conv_ORS() {
exec tr "$NL" "$1"
}
IN="bla#some.com;john#home.com"
IN="$(conv_IRS ";" <<< "$IN")"
while read i; do
# process "$i" ... eg.
echo -n "[email:$i]$ORS"
done <<< "$IN"
In both cases a sub-list can be composed within the loop is persistent after the loop has completed. This is useful when manipulating lists in memory, instead storing lists in files. {p.s. keep calm and carry on B-) }
In Android shell, most of the proposed methods just do not work:
$ IFS=':' read -ra ADDR <<<"$PATH"
/system/bin/sh: can't create temporary file /sqlite_stmt_journals/mksh.EbNoR10629: No such file or directory
What does work is:
$ for i in ${PATH//:/ }; do echo $i; done
/sbin
/vendor/bin
/system/sbin
/system/bin
/system/xbin
where // means global replacement.
IN='bla#some.com;john#home.com;Charlie Brown <cbrown#acme.com;!"#$%&/()[]{}*? are no problem;simple is beautiful :-)'
set -f
oldifs="$IFS"
IFS=';'; arrayIN=($IN)
IFS="$oldifs"
for i in "${arrayIN[#]}"; do
echo "$i"
done
set +f
Output:
bla#some.com
john#home.com
Charlie Brown <cbrown#acme.com
!"#$%&/()[]{}*? are no problem
simple is beautiful :-)
Explanation: Simple assignment using parenthesis () converts semicolon separated list into an array provided you have correct IFS while doing that. Standard FOR loop handles individual items in that array as usual.
Notice that the list given for IN variable must be "hard" quoted, that is, with single ticks.
IFS must be saved and restored since Bash does not treat an assignment the same way as a command. An alternate workaround is to wrap the assignment inside a function and call that function with a modified IFS. In that case separate saving/restoring of IFS is not needed. Thanks for "Bize" for pointing that out.
Here's my answer!
DELIMITER_VAL='='
read -d '' F_ABOUT_DISTRO_R <<"EOF"
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=14.04
DISTRIB_CODENAME=trusty
DISTRIB_DESCRIPTION="Ubuntu 14.04.4 LTS"
NAME="Ubuntu"
VERSION="14.04.4 LTS, Trusty Tahr"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 14.04.4 LTS"
VERSION_ID="14.04"
HOME_URL="http://www.ubuntu.com/"
SUPPORT_URL="http://help.ubuntu.com/"
BUG_REPORT_URL="http://bugs.launchpad.net/ubuntu/"
EOF
SPLIT_NOW=$(awk -F$DELIMITER_VAL '{for(i=1;i<=NF;i++){printf "%s\n", $i}}' <<<"${F_ABOUT_DISTRO_R}")
while read -r line; do
SPLIT+=("$line")
done <<< "$SPLIT_NOW"
for i in "${SPLIT[#]}"; do
echo "$i"
done
Why this approach is "the best" for me?
Because of two reasons:
You do not need to escape the delimiter;
You will not have problem with blank spaces. The value will be properly separated in the array.
A one-liner to split a string separated by ';' into an array is:
IN="bla#some.com;john#home.com"
ADDRS=( $(IFS=";" echo "$IN") )
echo ${ADDRS[0]}
echo ${ADDRS[1]}
This only sets IFS in a subshell, so you don't have to worry about saving and restoring its value.
I have this string stored in a variable:
IN="bla#some.com;john#home.com"
Now I would like to split the strings by ; delimiter so that I have:
ADDR1="bla#some.com"
ADDR2="john#home.com"
I don't necessarily need the ADDR1 and ADDR2 variables. If they are elements of an array that's even better.
After suggestions from the answers below, I ended up with the following which is what I was after:
#!/usr/bin/env bash
IN="bla#some.com;john#home.com"
mails=$(echo $IN | tr ";" "\n")
for addr in $mails
do
echo "> [$addr]"
done
Output:
> [bla#some.com]
> [john#home.com]
There was a solution involving setting Internal_field_separator (IFS) to ;. I am not sure what happened with that answer, how do you reset IFS back to default?
RE: IFS solution, I tried this and it works, I keep the old IFS and then restore it:
IN="bla#some.com;john#home.com"
OIFS=$IFS
IFS=';'
mails2=$IN
for x in $mails2
do
echo "> [$x]"
done
IFS=$OIFS
BTW, when I tried
mails2=($IN)
I only got the first string when printing it in loop, without brackets around $IN it works.
You can set the internal field separator (IFS) variable, and then let it parse into an array. When this happens in a command, then the assignment to IFS only takes place to that single command's environment (to read ). It then parses the input according to the IFS variable value into an array, which we can then iterate over.
This example will parse one line of items separated by ;, pushing it into an array:
IFS=';' read -ra ADDR <<< "$IN"
for i in "${ADDR[#]}"; do
# process "$i"
done
This other example is for processing the whole content of $IN, each time one line of input separated by ;:
while IFS=';' read -ra ADDR; do
for i in "${ADDR[#]}"; do
# process "$i"
done
done <<< "$IN"
Taken from Bash shell script split array:
IN="bla#some.com;john#home.com"
arrIN=(${IN//;/ })
echo ${arrIN[1]} # Output: john#home.com
Explanation:
This construction replaces all occurrences of ';' (the initial // means global replace) in the string IN with ' ' (a single space), then interprets the space-delimited string as an array (that's what the surrounding parentheses do).
The syntax used inside of the curly braces to replace each ';' character with a ' ' character is called Parameter Expansion.
There are some common gotchas:
If the original string has spaces, you will need to use IFS:
IFS=':'; arrIN=($IN); unset IFS;
If the original string has spaces and the delimiter is a new line, you can set IFS with:
IFS=$'\n'; arrIN=($IN); unset IFS;
I've seen a couple of answers referencing the cut command, but they've all been deleted. It's a little odd that nobody has elaborated on that, because I think it's one of the more useful commands for doing this type of thing, especially for parsing delimited log files.
In the case of splitting this specific example into a bash script array, tr is probably more efficient, but cut can be used, and is more effective if you want to pull specific fields from the middle.
Example:
$ echo "bla#some.com;john#home.com" | cut -d ";" -f 1
bla#some.com
$ echo "bla#some.com;john#home.com" | cut -d ";" -f 2
john#home.com
You can obviously put that into a loop, and iterate the -f parameter to pull each field independently.
This gets more useful when you have a delimited log file with rows like this:
2015-04-27|12345|some action|an attribute|meta data
cut is very handy to be able to cat this file and select a particular field for further processing.
If you don't mind processing them immediately, I like to do this:
for i in $(echo $IN | tr ";" "\n")
do
# process
done
You could use this kind of loop to initialize an array, but there's probably an easier way to do it.
Compatible answer
There are a lot of different ways to do this in bash.
However, it's important to first note that bash has many special features (so-called bashisms) that won't work in any other shell.
In particular, arrays, associative arrays, and pattern substitution, which are used in the solutions in this post as well as others in the thread, are bashisms and may not work under other shells that many people use.
For instance: on my Debian GNU/Linux, there is a standard shell called dash; I know many people who like to use another shell called ksh; and there is also a special tool called busybox with his own shell interpreter (ash).
For posix shell compatible answer, go to last part of this answer!
Requested string
The string to be split in the above question is:
IN="bla#some.com;john#home.com"
I will use a modified version of this string to ensure that my solution is robust to strings containing whitespace, which could break other solutions:
IN="bla#some.com;john#home.com;Full Name <fulnam#other.org>"
Split string based on delimiter in bash (version >=4.2)
In pure bash, we can create an array with elements split by a temporary value for IFS (the input field separator). The IFS, among other things, tells bash which character(s) it should treat as a delimiter between elements when defining an array:
IN="bla#some.com;john#home.com;Full Name <fulnam#other.org>"
# save original IFS value so we can restore it later
oIFS="$IFS"
IFS=";"
declare -a fields=($IN)
IFS="$oIFS"
unset oIFS
In newer versions of bash, prefixing a command with an IFS definition changes the IFS for that command only and resets it to the previous value immediately afterwards. This means we can do the above in just one line:
IFS=\; read -a fields <<<"$IN"
# after this command, the IFS resets back to its previous value (here, the default):
set | grep ^IFS=
# IFS=$' \t\n'
We can see that the string IN has been stored into an array named fields, split on the semicolons:
set | grep ^fields=\\\|^IN=
# fields=([0]="bla#some.com" [1]="john#home.com" [2]="Full Name <fulnam#other.org>")
# IN='bla#some.com;john#home.com;Full Name <fulnam#other.org>'
(We can also display the contents of these variables using declare -p:)
declare -p IN fields
# declare -- IN="bla#some.com;john#home.com;Full Name <fulnam#other.org>"
# declare -a fields=([0]="bla#some.com" [1]="john#home.com" [2]="Full Name <fulnam#other.org>")
Note that read is the quickest way to do the split because there are no forks or external resources called.
Once the array is defined, you can use a simple loop to process each field (or, rather, each element in the array you've now defined):
# `"${fields[#]}"` expands to return every element of `fields` array as a separate argument
for x in "${fields[#]}" ;do
echo "> [$x]"
done
# > [bla#some.com]
# > [john#home.com]
# > [Full Name <fulnam#other.org>]
Or you could drop each field from the array after processing using a shifting approach, which I like:
while [ "$fields" ] ;do
echo "> [$fields]"
# slice the array
fields=("${fields[#]:1}")
done
# > [bla#some.com]
# > [john#home.com]
# > [Full Name <fulnam#other.org>]
And if you just want a simple printout of the array, you don't even need to loop over it:
printf "> [%s]\n" "${fields[#]}"
# > [bla#some.com]
# > [john#home.com]
# > [Full Name <fulnam#other.org>]
Update: recent bash >= 4.4
In newer versions of bash, you can also play with the command mapfile:
mapfile -td \; fields < <(printf "%s\0" "$IN")
This syntax preserve special chars, newlines and empty fields!
If you don't want to include empty fields, you could do the following:
mapfile -td \; fields <<<"$IN"
fields=("${fields[#]%$'\n'}") # drop '\n' added by '<<<'
With mapfile, you can also skip declaring an array and implicitly "loop" over the delimited elements, calling a function on each:
myPubliMail() {
printf "Seq: %6d: Sending mail to '%s'..." $1 "$2"
# mail -s "This is not a spam..." "$2" </path/to/body
printf "\e[3D, done.\n"
}
mapfile < <(printf "%s\0" "$IN") -td \; -c 1 -C myPubliMail
(Note: the \0 at end of the format string is useless if you don't care about empty fields at end of the string or they're not present.)
mapfile < <(echo -n "$IN") -td \; -c 1 -C myPubliMail
# Seq: 0: Sending mail to 'bla#some.com', done.
# Seq: 1: Sending mail to 'john#home.com', done.
# Seq: 2: Sending mail to 'Full Name <fulnam#other.org>', done.
Or you could use <<<, and in the function body include some processing to drop the newline it adds:
myPubliMail() {
local seq=$1 dest="${2%$'\n'}"
printf "Seq: %6d: Sending mail to '%s'..." $seq "$dest"
# mail -s "This is not a spam..." "$dest" </path/to/body
printf "\e[3D, done.\n"
}
mapfile <<<"$IN" -td \; -c 1 -C myPubliMail
# Renders the same output:
# Seq: 0: Sending mail to 'bla#some.com', done.
# Seq: 1: Sending mail to 'john#home.com', done.
# Seq: 2: Sending mail to 'Full Name <fulnam#other.org>', done.
Split string based on delimiter in shell
If you can't use bash, or if you want to write something that can be used in many different shells, you often can't use bashisms -- and this includes the arrays we've been using in the solutions above.
However, we don't need to use arrays to loop over "elements" of a string. There is a syntax used in many shells for deleting substrings of a string from the first or last occurrence of a pattern. Note that * is a wildcard that stands for zero or more characters:
(The lack of this approach in any solution posted so far is the main reason I'm writing this answer ;)
${var#*SubStr} # drops substring from start of string up to first occurrence of `SubStr`
${var##*SubStr} # drops substring from start of string up to last occurrence of `SubStr`
${var%SubStr*} # drops substring from last occurrence of `SubStr` to end of string
${var%%SubStr*} # drops substring from first occurrence of `SubStr` to end of string
As explained by Score_Under:
# and % delete the shortest possible matching substring from the start and end of the string respectively, and
## and %% delete the longest possible matching substring.
Using the above syntax, we can create an approach where we extract substring "elements" from the string by deleting the substrings up to or after the delimiter.
The codeblock below works well in bash (including Mac OS's bash), dash, ksh, lksh, yash, zsh, and busybox's ash:
(Thanks to Adam Katz's comment, making this loop a lot simplier!)
IN="bla#some.com;john#home.com;Full Name <fulnam#other.org>"
while [ "$IN" != "$iter" ] ;do
# extract the substring from start of string up to delimiter.
iter=${IN%%;*}
# delete this first "element" AND next separator, from $IN.
IN="${IN#$iter;}"
# Print (or doing anything with) the first "element".
printf '> [%s]\n' "$iter"
done
# > [bla#some.com]
# > [john#home.com]
# > [Full Name <fulnam#other.org>]
Why not cut?
cut is usefull for extracting columns in big files, but doing forks repetitively (var=$(echo ... | cut ...)) become quickly overkill!
Here is a correct syntax, tested under many posix shell using cut, as suggested by This other answer from DougW:
IN="bla#some.com;john#home.com;Full Name <fulnam#other.org>"
i=1
while iter=$(echo "$IN"|cut -d\; -f$i) ; [ -n "$iter" ] ;do
printf '> [%s]\n' "$iter"
i=$((i+1))
done
I wrote this in order to compare execution time.
On my raspberrypi, this look like:
$ export TIMEFORMAT=$'(%U + %S) / \e[1m%R\e[0m : %P '
$ time sh splitDemo.sh >/dev/null
(0.000 + 0.019) / 0.019 : 99.63
$ time sh splitDemo_cut.sh >/dev/null
(0.051 + 0.041) / 0.188 : 48.98
Where overall execution time is something like 10x longer, using 1 forks to cut, by field!
This worked for me:
string="1;2"
echo $string | cut -d';' -f1 # output is 1
echo $string | cut -d';' -f2 # output is 2
I think AWK is the best and efficient command to resolve your problem. AWK is included by default in almost every Linux distribution.
echo "bla#some.com;john#home.com" | awk -F';' '{print $1,$2}'
will give
bla#some.com john#home.com
Of course your can store each email address by redefining the awk print field.
How about this approach:
IN="bla#some.com;john#home.com"
set -- "$IN"
IFS=";"; declare -a Array=($*)
echo "${Array[#]}"
echo "${Array[0]}"
echo "${Array[1]}"
Source
echo "bla#some.com;john#home.com" | sed -e 's/;/\n/g'
bla#some.com
john#home.com
This also works:
IN="bla#some.com;john#home.com"
echo ADD1=`echo $IN | cut -d \; -f 1`
echo ADD2=`echo $IN | cut -d \; -f 2`
Be careful, this solution is not always correct. In case you pass "bla#some.com" only, it will assign it to both ADD1 and ADD2.
A different take on Darron's answer, this is how I do it:
IN="bla#some.com;john#home.com"
read ADDR1 ADDR2 <<<$(IFS=";"; echo $IN)
How about this one liner, if you're not using arrays:
IFS=';' read ADDR1 ADDR2 <<<$IN
In Bash, a bullet proof way, that will work even if your variable contains newlines:
IFS=';' read -d '' -ra array < <(printf '%s;\0' "$in")
Look:
$ in=$'one;two three;*;there is\na newline\nin this field'
$ IFS=';' read -d '' -ra array < <(printf '%s;\0' "$in")
$ declare -p array
declare -a array='([0]="one" [1]="two three" [2]="*" [3]="there is
a newline
in this field")'
The trick for this to work is to use the -d option of read (delimiter) with an empty delimiter, so that read is forced to read everything it's fed. And we feed read with exactly the content of the variable in, with no trailing newline thanks to printf. Note that's we're also putting the delimiter in printf to ensure that the string passed to read has a trailing delimiter. Without it, read would trim potential trailing empty fields:
$ in='one;two;three;' # there's an empty field
$ IFS=';' read -d '' -ra array < <(printf '%s;\0' "$in")
$ declare -p array
declare -a array='([0]="one" [1]="two" [2]="three" [3]="")'
the trailing empty field is preserved.
Update for Bash≥4.4
Since Bash 4.4, the builtin mapfile (aka readarray) supports the -d option to specify a delimiter. Hence another canonical way is:
mapfile -d ';' -t array < <(printf '%s;' "$in")
Without setting the IFS
If you just have one colon you can do that:
a="foo:bar"
b=${a%:*}
c=${a##*:}
you will get:
b = foo
c = bar
Here is a clean 3-liner:
in="foo#bar;bizz#buzz;fizz#buzz;buzz#woof"
IFS=';' list=($in)
for item in "${list[#]}"; do echo $item; done
where IFS delimit words based on the separator and () is used to create an array. Then [#] is used to return each item as a separate word.
If you've any code after that, you also need to restore $IFS, e.g. unset IFS.
The following Bash/zsh function splits its first argument on the delimiter given by the second argument:
split() {
local string="$1"
local delimiter="$2"
if [ -n "$string" ]; then
local part
while read -d "$delimiter" part; do
echo $part
done <<< "$string"
echo $part
fi
}
For instance, the command
$ split 'a;b;c' ';'
yields
a
b
c
This output may, for instance, be piped to other commands. Example:
$ split 'a;b;c' ';' | cat -n
1 a
2 b
3 c
Compared to the other solutions given, this one has the following advantages:
IFS is not overriden: Due to dynamic scoping of even local variables, overriding IFS over a loop causes the new value to leak into function calls performed from within the loop.
Arrays are not used: Reading a string into an array using read requires the flag -a in Bash and -A in zsh.
If desired, the function may be put into a script as follows:
#!/usr/bin/env bash
split() {
# ...
}
split "$#"
you can apply awk to many situations
echo "bla#some.com;john#home.com"|awk -F';' '{printf "%s\n%s\n", $1, $2}'
also you can use this
echo "bla#some.com;john#home.com"|awk -F';' '{print $1,$2}' OFS="\n"
There is a simple and smart way like this:
echo "add:sfff" | xargs -d: -i echo {}
But you must use gnu xargs, BSD xargs cant support -d delim. If you use apple mac like me. You can install gnu xargs :
brew install findutils
then
echo "add:sfff" | gxargs -d: -i echo {}
There are some cool answers here (errator esp.), but for something analogous to split in other languages -- which is what I took the original question to mean -- I settled on this:
IN="bla#some.com;john#home.com"
declare -a a="(${IN//;/ })";
Now ${a[0]}, ${a[1]}, etc, are as you would expect. Use ${#a[*]} for number of terms. Or to iterate, of course:
for i in ${a[*]}; do echo $i; done
IMPORTANT NOTE:
This works in cases where there are no spaces to worry about, which solved my problem, but may not solve yours. Go with the $IFS solution(s) in that case.
So many answers and so many complexities. Try out a simpler solution:
echo "string1, string2" | tr , "\n"
tr (read, translate) replaces the first argument with the second argument in the input.
So tr , "\n" replace the comma with new line character in the input and it becomes:
string1
string2
If no space, Why not this?
IN="bla#some.com;john#home.com"
arr=(`echo $IN | tr ';' ' '`)
echo ${arr[0]}
echo ${arr[1]}
This is the simplest way to do it.
spo='one;two;three'
OIFS=$IFS
IFS=';'
spo_array=($spo)
IFS=$OIFS
echo ${spo_array[*]}
Apart from the fantastic answers that were already provided, if it is just a matter of printing out the data you may consider using awk:
awk -F";" '{for (i=1;i<=NF;i++) printf("> [%s]\n", $i)}' <<< "$IN"
This sets the field separator to ;, so that it can loop through the fields with a for loop and print accordingly.
Test
$ IN="bla#some.com;john#home.com"
$ awk -F";" '{for (i=1;i<=NF;i++) printf("> [%s]\n", $i)}' <<< "$IN"
> [bla#some.com]
> [john#home.com]
With another input:
$ awk -F";" '{for (i=1;i<=NF;i++) printf("> [%s]\n", $i)}' <<< "a;b;c d;e_;f"
> [a]
> [b]
> [c d]
> [e_]
> [f]
IN="bla#some.com;john#home.com"
IFS=';'
read -a IN_arr <<< "${IN}"
for entry in "${IN_arr[#]}"
do
echo $entry
done
Output
bla#some.com
john#home.com
System : Ubuntu 12.04.1
Use the set built-in to load up the $# array:
IN="bla#some.com;john#home.com"
IFS=';'; set $IN; IFS=$' \t\n'
Then, let the party begin:
echo $#
for a; do echo $a; done
ADDR1=$1 ADDR2=$2
Two bourne-ish alternatives where neither require bash arrays:
Case 1: Keep it nice and simple: Use a NewLine as the Record-Separator... eg.
IN="bla#some.com
john#home.com"
while read i; do
# process "$i" ... eg.
echo "[email:$i]"
done <<< "$IN"
Note: in this first case no sub-process is forked to assist with list manipulation.
Idea: Maybe it is worth using NL extensively internally, and only converting to a different RS when generating the final result externally.
Case 2: Using a ";" as a record separator... eg.
NL="
" IRS=";" ORS=";"
conv_IRS() {
exec tr "$1" "$NL"
}
conv_ORS() {
exec tr "$NL" "$1"
}
IN="bla#some.com;john#home.com"
IN="$(conv_IRS ";" <<< "$IN")"
while read i; do
# process "$i" ... eg.
echo -n "[email:$i]$ORS"
done <<< "$IN"
In both cases a sub-list can be composed within the loop is persistent after the loop has completed. This is useful when manipulating lists in memory, instead storing lists in files. {p.s. keep calm and carry on B-) }
In Android shell, most of the proposed methods just do not work:
$ IFS=':' read -ra ADDR <<<"$PATH"
/system/bin/sh: can't create temporary file /sqlite_stmt_journals/mksh.EbNoR10629: No such file or directory
What does work is:
$ for i in ${PATH//:/ }; do echo $i; done
/sbin
/vendor/bin
/system/sbin
/system/bin
/system/xbin
where // means global replacement.
IN='bla#some.com;john#home.com;Charlie Brown <cbrown#acme.com;!"#$%&/()[]{}*? are no problem;simple is beautiful :-)'
set -f
oldifs="$IFS"
IFS=';'; arrayIN=($IN)
IFS="$oldifs"
for i in "${arrayIN[#]}"; do
echo "$i"
done
set +f
Output:
bla#some.com
john#home.com
Charlie Brown <cbrown#acme.com
!"#$%&/()[]{}*? are no problem
simple is beautiful :-)
Explanation: Simple assignment using parenthesis () converts semicolon separated list into an array provided you have correct IFS while doing that. Standard FOR loop handles individual items in that array as usual.
Notice that the list given for IN variable must be "hard" quoted, that is, with single ticks.
IFS must be saved and restored since Bash does not treat an assignment the same way as a command. An alternate workaround is to wrap the assignment inside a function and call that function with a modified IFS. In that case separate saving/restoring of IFS is not needed. Thanks for "Bize" for pointing that out.
Here's my answer!
DELIMITER_VAL='='
read -d '' F_ABOUT_DISTRO_R <<"EOF"
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=14.04
DISTRIB_CODENAME=trusty
DISTRIB_DESCRIPTION="Ubuntu 14.04.4 LTS"
NAME="Ubuntu"
VERSION="14.04.4 LTS, Trusty Tahr"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 14.04.4 LTS"
VERSION_ID="14.04"
HOME_URL="http://www.ubuntu.com/"
SUPPORT_URL="http://help.ubuntu.com/"
BUG_REPORT_URL="http://bugs.launchpad.net/ubuntu/"
EOF
SPLIT_NOW=$(awk -F$DELIMITER_VAL '{for(i=1;i<=NF;i++){printf "%s\n", $i}}' <<<"${F_ABOUT_DISTRO_R}")
while read -r line; do
SPLIT+=("$line")
done <<< "$SPLIT_NOW"
for i in "${SPLIT[#]}"; do
echo "$i"
done
Why this approach is "the best" for me?
Because of two reasons:
You do not need to escape the delimiter;
You will not have problem with blank spaces. The value will be properly separated in the array.
A one-liner to split a string separated by ';' into an array is:
IN="bla#some.com;john#home.com"
ADDRS=( $(IFS=";" echo "$IN") )
echo ${ADDRS[0]}
echo ${ADDRS[1]}
This only sets IFS in a subshell, so you don't have to worry about saving and restoring its value.
I am trying to parse a huge text file, say 200mb.
the text file contains some strings
123
1234
12345
12345
so my script looked like
while read line ; do
echo "$line"
done <textfile
however using this above method, my string " 12345" gets truncated to "12345"
I tried using
sed -n "$i"p textfile
but the the throughput is reduced from 27 to 0.2 lines per second, which is inacceptable ;-)
any Idea howto solve this?
You want to echo the lines without a fieldsep:
while IFS="" read line; do
echo "$line"
done <<< " 12345"
When you also want to skip interpretation of special characters, use
while IFS="" read -r line; do
echo "$line"
done <<< " 12345"
You can write the IFS without double quotes:
while IFS= read -r line; do
echo "$line"
done <<< " 12345"
This seems to be what you're looking for:
while IFS= read line; do
echo "$line"
done < textfile
The safest method is to use read -r in comparison to just read which will skip interpretation of special characters (thanks Walter A):
while IFS= read -r line; do
echo "$line"
done < textfile
OPTION 1:
#!/bin/bash
# read whole file into array
readarray -t aMyArray < <(cat textfile)
# echo each line of the array
# this will preserve spaces
for i in "${aMyArray[#]}"; do echo "$i"; done
readarray -- read lines from standard input
-t -- omit trailing newline character
aMyArray -- name of array to store file in
< <() -- execute command; redirect stdout into array
cat textfile -- file you want to store in variable
for i in "${aMyArray[#]}" -- for every element in aMyArray
"" -- needed to maintain spaces in elements
${ [#]} -- reference all elements in array
do echo "$i"; -- for every iteration of "$i" echo it
"" -- to maintain variable spaces
$i -- equals each element of the array aMyArray as it cycles through
done -- close for loop
OPTION 2:
In order to accommodate your larger file you could do this to help alleviate the work and speed up the processing.
#!/bin/bash
sSearchFile=textfile
sSearchStrings="1|2|3|space"
while IFS= read -r line; do
echo "${line}"
done < <(egrep "${sSearchStrings}" "${sSearchFile}")
This will grep the file (faster) before it cycles it through the while command. Let me know how this works for you. Notice you can add multiple search strings to the $sSearchStrings variable.
OPTION 3:
and an all in one solution to have a text file with your search criteria and everything else combined...
#!/bin/bash
# identify file containing search strings
sSearchStrings="searchstrings.file"
while IFS= read -r string; do
# if $sSearchStrings empty read in strings
[[ -z $sSearchStrings ]] && sSearchStrings="${string}"
# if $sSearchStrings not empty read in $sSearchStrings "|" $string
[[ ! -z $sSearchStrings ]] && sSearchStrings="${sSearchStrings}|${string}"
# read search criteria in from file
done <"${sSearchStrings}"
# identify file to be searched
sSearchFile="text.file"
while IFS= read -r line; do
echo "${line}"
done < <(egrep "${sSearchStrings}" "${sSearchFile}")
I have a script variable which is multi-line.
How do i traverse this variable to read it line by line and process each line the way I want?
Consider the following multi-line variable
x=$(echo -e "a\nb\nc d e")
and a simple process for each line: just echo it with a prefix=LINE: and with single quotes around the line. Either of the following codes will satisfy that requirement:
while read line; do echo "LINE: '${line}'"; done <<< "$x"
or
while read line; do echo "LINE: '${line}'"; done < <(echo "$x")
Neither creates a subshell (so you can, e.g., set variables in the loop and access them outside of it), and both output
LINE: 'a'
LINE: 'b'
LINE: 'c d e'
But suppose instead you have
x=$(echo -e "a \n b\nc d e")
# note--------^--^
and that leading and trailing whitespace matter for your application (e.g., parsing Git porcelain). Both the above codes will give exactly the same output for the latter variable/data as for the former, which is not what you want. To preserve leading and trailing whitespace, replace while read line with while IFS= read -r line . I.e., either of the following codes
while IFS= read -r line; do echo "LINE: '${line}'"; done <<< "$x"
or
while IFS= read -r line; do echo "LINE: '${line}'"; done < <(echo "$x")
will produce
LINE: 'a '
LINE: ' b'
LINE: 'c d e'
See Greg Wooledge's excellent Bash FAQ for details.
Although I typically use "while read" for processing multi-line variables, I recently had an instance where it removed the leading space from each line in a file. Using this instead fixed my issue:
printf '%s\n' "$var" | while IFS= read -r line
do
echo "$line"
done
Code taken from this Unix Stack Exchange answer.
Edit: updated to fix last line issue as suggested by Nicolae Iotu
If I have a file like this:
A:a
B:b
C:c
I need to create 2 arrays like
one=('A' 'B' 'C')
two=('a' 'b' 'c')
How can I do it in bash?
I've tried this:
declare -a one
declare -a two
while read line
do
IFS=':' read -ra ADDR <<< $line
echo ${ADDR[0]}
echo ${ADDR[1]}
done < file.txt
Sorry I wrote from work and then I came home. Sorry again. The problem with this is that it's printing
littlelion:Documents dierre$ sh prova.sh
A a
B b
so it's missing C c and I have no idea how to add an element to an array
Quotes fix everything:
while read line
do
IFS=':' read -ra ADDR <<< "$line"
echo ${ADDR[0]}
echo ${ADDR[1]}
done < file.txt
Quoting the variable "$line" is what made the difference. If you're not getting the line with "C:c", it's probably because your file is missing a final newline.
If I understand what you're trying to do properly, this should work:
one=()
two=()
while IFS=: read new_one new_two || [ -n "$new_one" ]; do
one+=("$new_one")
two+=("$new_two")
done
echo "one:" "${one[#]}"
echo "two:" "${two[#]}"
Note: I agree with #Dennis Williamson that the final line isn't being processed because it doesn't end with a newline; I added the || [ -n "$new_one" ] bit to keep this from being a problem.
Use Command Substitution:
declare -a one
declare -a two
one=( $(cut -d: -f1 file) )
two=( $(cut -d: -f2 file) )
var=$(command) captures the output of your command and assigns it to var. The outer parens makes that an array assignment. cut -d: -f1 says to treat your file as a colon delimited file and print the first field. cut -d: -f2 does the same but it prints the second field.
Edit in response to OP's edits
You can read into ADDR directly like so:
declare -a ADDR
while IFS=':' read -a ADDR; do
echo ${ADDR[0]}
echo ${ADDR[1]}
done < file.txt
Although that won't populate arrays one and two...