How to split a string into an array in Bash

Question

In a Bash script  I would like to split a line into pieces and store them in an array  For example  given the line  Paris  France  Europe  I would like to have the resulting array to look like so  array 0    Paris array 1    France array 2    Europe  A simple implementation is preferable  speed does not matter  How can I do it

User · Answer

Here is a way without setting IFS   string  1 2 3 4 5  set -f                        avoid globbing  expansion of     array    string        for i in     array      do     echo   i  gt   array i    done   The idea is using string replacement     string  substring replacement    to replace all matches of  substring with white space and then using the substituted string to initialize a array    element1 element2     elementN    Note  this answer makes use of the split glob operator  Thus  to prevent expansion of some characters  such as    it is a good idea to pause globbing for this script

User · Answer

IFS      read -r -a array  lt  lt  lt    string    Note that the characters in  IFS are treated individually as separators so that in this case fields may be separated by either a comma or a space rather than the sequence of the two characters  Interestingly though  empty fields aren t created when comma-space appears in the input because the space is treated specially   To access an individual element   echo    array 0      To iterate over the elements   for element in    array      do     echo   element  done   To get both the index and the value   for index in     array      do     echo   index   array index    done   The last example is useful because Bash arrays are sparse  In other words  you can delete an element or add an element and then the indices are not contiguous   unset  array 1   array 42  Earth   To get the number of elements in an array   echo     array        As mentioned above  arrays can be sparse so you shouldn t use the length to get the last element  Here s how you can in Bash 4 2 and later   echo    array -1      in any version of Bash  from somewhere after 2 05b    echo    array     -1 1     Larger negative offsets select farther from the end of the array  Note the space before the minus sign in the older form  It is required

User · Answer

Use this   countries  Paris  France  Europe  OIFS   IFS  IFS      array   countries  IFS   OIFS      array 1      Paris    array 2      France    array 3      Europe

User · Answer

All of the answers to this question are wrong in one way or another     Wrong answer  1  IFS      read -r -a array  lt  lt  lt    string    1  This is a misuse of  IFS  The value of the  IFS variable is not taken as a single variable-length string separator  rather it is taken as a set of single-character string separators  where each field that read splits off from the input line can be terminated by any character in the set  comma or space  in this example    Actually  for the real sticklers out there  the full meaning of  IFS is slightly more involved  From the bash manual      The shell treats each character of IFS as a delimiter  and splits the results of the other expansions into words using these characters as field terminators  If IFS is unset  or its value is exactly  lt space gt  lt tab gt  lt newline gt   the default  then sequences of  lt space gt    lt tab gt   and  lt newline gt  at the beginning and end of the results of the previous expansions are ignored  and any sequence of IFS characters not at the beginning or end serves to delimit words  If IFS has a value other than the default  then sequences of the whitespace characters  lt space gt    lt tab gt   and  lt newline gt  are ignored at the beginning and end of the word  as long as the whitespace character is in the value of IFS  an IFS whitespace character   Any character in IFS that is not IFS whitespace  along with any adjacent IFS whitespace characters  delimits a field  A sequence of IFS whitespace characters is also treated as a delimiter  If the value of IFS is null  no word splitting occurs    Basically  for non-default non-null values of  IFS  fields can be separated with either  1  a sequence of one or more characters that are all from the set of  IFS whitespace characters   that is  whichever of  lt space gt    lt tab gt   and  lt newline gt    newline  meaning line feed  LF   are present anywhere in  IFS   or  2  any non- IFS whitespace character  that s present in  IFS along with whatever  IFS whitespace characters  surround it in the input line   For the OP  it s possible that the second separation mode I described in the previous paragraph is exactly what he wants for his input string  but we can be pretty confident that the first separation mode I described is not correct at all  For example  what if his input string was  Los Angeles  United States  North America    IFS      read -ra a  lt  lt  lt  Los Angeles  United States  North America   declare -p a     declare -a a   0   Los   1   Angeles   2   United   3   States   4   North   5   America     2  Even if you were to use this solution with a single-character separator  such as a comma by itself  that is  with no following space or other baggage   if the value of the  string variable happens to contain any LFs  then read will stop processing once it encounters the first LF  The read builtin only processes one line per invocation  This is true even if you are piping or redirecting input only to the read statement  as we are doing in this example with the here-string mechanism  and thus unprocessed input is guaranteed to be lost  The code that powers the read builtin has no knowledge of the data flow within its containing command structure   You could argue that this is unlikely to cause a problem  but still  it s a subtle hazard that should be avoided if possible  It is caused by the fact that the read builtin actually does two levels of input splitting  first into lines  then into fields  Since the OP only wants one level of splitting  this usage of the read builtin is not appropriate  and we should avoid it   3  A non-obvious potential issue with this solution is that read always drops the trailing field if it is empty  although it preserves empty fields otherwise  Here s a demo   string      a    b  c         IFS      read -ra a  lt  lt  lt   string   declare -p a     declare -a a   0      1      2   a   3      4   b   5   c   6      7        Maybe the OP wouldn t care about this  but it s still a limitation worth knowing about  It reduces the robustness and generality of the solution   This problem can be solved by appending a dummy trailing delimiter to the input string just prior to feeding it to read  as I will demonstrate later     Wrong answer  2  string  1 2 3 4 5  set -f                       avoid globbing  expansion of     array    string          Similar idea   t  one two three  a    echo  t   tr       n       Note  I added the missing parentheses around the command substitution which the answerer seems to have omitted    Similar idea   string  1 2 3 4  array   echo  string   sed  s    n g      These solutions leverage word splitting in an array assignment to split the string into fields  Funnily enough  just like read  general word splitting also uses the  IFS special variable  although in this case it is implied that it is set to its default value of  lt space gt  lt tab gt  lt newline gt   and therefore any sequence of one or more IFS characters  which are all whitespace characters now  is considered to be a field delimiter   This solves the problem of two levels of splitting committed by read  since word splitting by itself constitutes only one level of splitting  But just as before  the problem here is that the individual fields in the input string can already contain  IFS characters  and thus they would be improperly split during the word splitting operation  This happens to not be the case for any of the sample input strings provided by these answerers  how convenient      but of course that doesn t change the fact that any code base that used this idiom would then run the risk of blowing up if this assumption were ever violated at some point down the line  Once again  consider my counterexample of  Los Angeles  United States  North America   or  Los Angeles United States North America     Also  word splitting is normally followed by filename expansion  aka pathname expansion aka globbing   which  if done  would potentially corrupt words containing the characters       or   followed by    and  if extglob is set  parenthesized fragments preceded by             or    by matching them against file system objects and expanding the words   globs   accordingly  The first of these three answerers has cleverly undercut this problem by running set -f beforehand to disable globbing  Technically this works  although you should probably add set  f afterward to reenable globbing for subsequent code which may depend on it   but it s undesirable to have to mess with global shell settings in order to hack a basic string-to-array parsing operation in local code   Another issue with this answer is that all empty fields will be lost  This may or may not be a problem  depending on the application   Note  If you re going to use this solution  it s better to use the   string        pattern substitution  form of parameter expansion  rather than going to the trouble of invoking a command substitution  which forks the shell   starting up a pipeline  and running an external executable  tr or sed   since parameter expansion is purely a shell-internal operation   Also  for the tr and sed solutions  the input variable should be double-quoted inside the command substitution  otherwise word splitting would take effect in the echo command and potentially mess with the field values  Also  the        form of command substitution is preferable to the old       form since it simplifies nesting of command substitutions and allows for better syntax highlighting by text editors      Wrong answer  3  str  a  b  c  d     assuming there is a space after     as in Q arr    str          delete all occurrences of       This answer is almost the same as  2  The difference is that the answerer has made the assumption that the fields are delimited by two characters  one of which being represented in the default  IFS  and the other not  He has solved this rather specific case by removing the non-IFS-represented character using a pattern substitution expansion and then using word splitting to split the fields on the surviving IFS-represented delimiter character   This is not a very generic solution  Furthermore  it can be argued that the comma is really the  primary  delimiter character here  and that stripping it and then depending on the space character for field splitting is simply wrong  Once again  consider my counterexample   Los Angeles  United States  North America    Also  again  filename expansion could corrupt the expanded words  but this can be prevented by temporarily disabling globbing for the assignment with set -f and then set  f   Also  again  all empty fields will be lost  which may or may not be a problem depending on the application     Wrong answer  4  string  first line second line third line   oldIFS   IFS  IFS     IFS   IFS 0 1    this is useful to format your code with tabs lines    string   IFS   oldIFS    This is similar to  2 and  3 in that it uses word splitting to get the job done  only now the code explicitly sets  IFS to contain only the single-character field delimiter present in the input string  It should be repeated that this cannot work for multicharacter field delimiters such as the OP s comma-space delimiter  But for a single-character delimiter like the LF used in this example  it actually comes close to being perfect  The fields cannot be unintentionally split in the middle as we saw with previous wrong answers  and there is only one level of splitting  as required   One problem is that filename expansion will corrupt affected words as described earlier  although once again this can be solved by wrapping the critical statement in set -f and set  f   Another potential problem is that  since LF qualifies as an  IFS whitespace character  as defined earlier  all empty fields will be lost  just as in  2 and  3  This would of course not be a problem if the delimiter happens to be a non- IFS whitespace character   and depending on the application it may not matter anyway  but it does vitiate the generality of the solution   So  to sum up  assuming you have a one-character delimiter  and it is either a non- IFS whitespace character  or you don t care about empty fields  and you wrap the critical statement in set -f and set  f  then this solution works  but otherwise not    Also  for information s sake  assigning a LF to a variable in bash can be done more easily with the        syntax  e g  IFS    n        Wrong answer  5  countries  Paris  France  Europe  OIFS   IFS  IFS      array   countries  IFS   OIFS    Similar idea   IFS      eval  array   string     This solution is effectively a cross between  1  in that it sets  IFS to comma-space  and  2-4  in that it uses word splitting to split the string into fields   Because of this  it suffers from most of the problems that afflict all of the above wrong answers  sort of like the worst of all worlds   Also  regarding the second variant  it may seem like the eval call is completely unnecessary  since its argument is a single-quoted string literal  and therefore is statically known  But there s actually a very non-obvious benefit to using eval in this way  Normally  when you run a simple command which consists of a variable assignment only  meaning without an actual command word following it  the assignment takes effect in the shell environment   IFS          changes  IFS in the shell environment   This is true even if the simple command involves multiple variable assignments  again  as long as there s no command word  all variable assignments affect the shell environment   IFS      array   countries      changes both  IFS and  array in the shell environment   But  if the variable assignment is attached to a command name  I like to call this a  prefix assignment   then it does not affect the shell environment  and instead only affects the environment of the executed command  regardless whether it is a builtin or external   IFS              is a builtin command  the  IFS assignment does not outlive it IFS      env     env is an external command  the  IFS assignment does not outlive it   Relevant quote from the bash manual      If no command name results  the variable assignments affect the current shell environment  Otherwise  the variables are added to the environment of the executed command and do not affect the current shell environment    It is possible to exploit this feature of variable assignment to change  IFS only temporarily  which allows us to avoid the whole save-and-restore gambit like that which is being done with the  OIFS variable in the first variant  But the challenge we face here is that the command we need to run is itself a mere variable assignment  and hence it would not involve a command word to make the  IFS assignment temporary  You might think to yourself  well why not just add a no-op command word to the statement like the   builtin to make the  IFS assignment temporary  This does not work because it would then make the  array assignment temporary as well   IFS      array   countries        fails  new  array value never escapes the   command   So  we re effectively at an impasse  a bit of a catch-22  But  when eval runs its code  it runs it in the shell environment  as if it was normal  static source code  and therefore we can run the  array assignment inside the eval argument to have it take effect in the shell environment  while the  IFS prefix assignment that is prefixed to the eval command will not outlive the eval command  This is exactly the trick that is being used in the second variant of this solution   IFS      eval  array   string        IFS does not outlive the eval command  but  array does   So  as you can see  it s actually quite a clever trick  and accomplishes exactly what is required  at least with respect to assignment effectation  in a rather non-obvious way  I m actually not against this trick in general  despite the involvement of eval  just be careful to single-quote the argument string to guard against security threats   But again  because of the  worst of all worlds  agglomeration of problems  this is still a wrong answer to the OP s requirement     Wrong answer  6  IFS       array  Paris  France  Europe   IFS     declare -a array  Paris France Europe    Um    what  The OP has a string variable that needs to be parsed into an array  This  answer  starts with the verbatim contents of the input string pasted into an array literal  I guess that s one way to do it   It looks like the answerer may have assumed that the  IFS variable affects all bash parsing in all contexts  which is not true  From the bash manual      IFS nbsp  nbsp  nbsp  nbsp The Internal Field Separator that is used for word splitting after expansion and to split lines into words with the read builtin command  The default value is  lt space gt  lt tab gt  lt newline gt     So the  IFS special variable is actually only used in two contexts   1  word splitting that is performed after expansion  meaning not when parsing bash source code  and  2  for splitting input lines into words by the read builtin   Let me try to make this clearer  I think it might be good to draw a distinction between parsing and execution  Bash must first parse the source code  which obviously is a parsing event  and then later it executes the code  which is when expansion comes into the picture  Expansion is really an execution event  Furthermore  I take issue with the description of the  IFS variable that I just quoted above  rather than saying that word splitting is performed after expansion  I would say that word splitting is performed during expansion  or  perhaps even more precisely  word splitting is part of the expansion process  The phrase  word splitting  refers only to this step of expansion  it should never be used to refer to the parsing of bash source code  although unfortunately the docs do seem to throw around the words  split  and  words  a lot  Here s a relevant excerpt from the linux die net version of the bash manual      Expansion is performed on the command line after it has been split into words  There are seven kinds of expansion performed  brace expansion  tilde expansion  parameter and variable expansion  command substitution  arithmetic expansion  word splitting  and pathname expansion       The order of expansions is  brace expansion  tilde expansion  parameter and variable expansion  arithmetic expansion  and command substitution  done in a left-to-right fashion   word splitting  and pathname expansion    You could argue the GNU version of the manual does slightly better  since it opts for the word  tokens  instead of  words  in the first sentence of the Expansion section      Expansion is performed on the command line after it has been split into tokens    The important point is   IFS does not change the way bash parses source code  Parsing of bash source code is actually a very complex process that involves recognition of the various elements of shell grammar  such as command sequences  command lists  pipelines  parameter expansions  arithmetic substitutions  and command substitutions  For the most part  the bash parsing process cannot be altered by user-level actions like variable assignments  actually  there are some minor exceptions to this rule  for example  see the various compatxx shell settings  which can change certain aspects of parsing behavior on-the-fly   The upstream  words   tokens  that result from this complex parsing process are then expanded according to the general process of  expansion  as broken down in the above documentation excerpts  where word splitting of the expanded  expanding   text into downstream words is simply one step of that process  Word splitting only touches text that has been spit out of a preceding expansion step  it does not affect literal text that was parsed right off the source bytestream     Wrong answer  7  string  first line         second line         third line   while read -r line  do lines     line    done  lt  lt  lt   string    This is one of the best solutions  Notice that we re back to using read  Didn t I say earlier that read is inappropriate because it performs two levels of splitting  when we only need one  The trick here is that you can call read in such a way that it effectively only does one level of splitting  specifically by splitting off only one field per invocation  which necessitates the cost of having to call it repeatedly in a loop  It s a bit of a sleight of hand  but it works   But there are problems  First  When you provide at least one NAME argument to read  it automatically ignores leading and trailing whitespace in each field that is split off from the input string  This occurs whether  IFS is set to its default value or not  as described earlier in this post  Now  the OP may not care about this for his specific use-case  and in fact  it may be a desirable feature of the parsing behavior  But not everyone who wants to parse a string into fields will want this  There is a solution  however  A somewhat non-obvious usage of read is to pass zero NAME arguments  In this case  read will store the entire input line that it gets from the input stream in a variable named  REPLY  and  as a bonus  it does not strip leading and trailing whitespace from the value  This is a very robust usage of read which I ve exploited frequently in my shell programming career  Here s a demonstration of the difference in behavior   string     a  b   n  c  d   n  e  f        input string  a     while read -r line  do a     line    done  lt  lt  lt   string   declare -p a     declare -a a   0   a  b   1   c  d   2   e  f      read trimmed surrounding whitespace  a     while read -r  do a     REPLY    done  lt  lt  lt   string   declare -p a     declare -a a   0     a  b     1     c  d     2     e  f        no trimming   The second issue with this solution is that it does not actually address the case of a custom field separator  such as the OP s comma-space  As before  multicharacter separators are not supported  which is an unfortunate limitation of this solution  We could try to at least split on comma by specifying the separator to the -d option  but look what happens   string  Paris  France  Europe   a     while read -rd   do a     REPLY    done  lt  lt  lt   string   declare -p a     declare -a a   0   Paris   1    France     Predictably  the unaccounted surrounding whitespace got pulled into the field values  and hence this would have to be corrected subsequently through trimming operations  this could also be done directly in the while-loop   But there s another obvious error  Europe is missing  What happened to it  The answer is that read returns a failing return code if it hits end-of-file  in this case we can call it end-of-string  without encountering a final field terminator on the final field  This causes the while-loop to break prematurely and we lose the final field   Technically this same error afflicted the previous examples as well  the difference there is that the field separator was taken to be LF  which is the default when you don t specify the -d option  and the  lt  lt  lt    here-string   mechanism automatically appends a LF to the string just before it feeds it as input to the command  Hence  in those cases  we sort of accidentally solved the problem of a dropped final field by unwittingly appending an additional dummy terminator to the input  Let s call this solution the  dummy-terminator  solution  We can apply the dummy-terminator solution manually for any custom delimiter by concatenating it against the input string ourselves when instantiating it in the here-string   a     while read -rd   do a     REPLY    done  lt  lt  lt   string    declare -p a  declare -a a   0   Paris   1    France   2    Europe     There  problem solved  Another solution is to only break the while-loop if both  1  read returned failure and  2   REPLY is empty  meaning read was not able to read any characters prior to hitting end-of-file  Demo   a     while read -rd       -n   REPLY      do a     REPLY    done  lt  lt  lt   string   declare -p a     declare -a a   0   Paris   1    France   2     Europe n     This approach also reveals the secretive LF that automatically gets appended to the here-string by the  lt  lt  lt  redirection operator  It could of course be stripped off separately through an explicit trimming operation as described a moment ago  but obviously the manual dummy-terminator approach solves it directly  so we could just go with that  The manual dummy-terminator solution is actually quite convenient in that it solves both of these two problems  the dropped-final-field problem and the appended-LF problem  in one go   So  overall  this is quite a powerful solution  It s only remaining weakness is a lack of support for multicharacter delimiters  which I will address later     Wrong answer  8  string  first line         second line         third line   readarray -t lines  lt  lt  lt   string     This is actually from the same post as  7  the answerer provided two solutions in the same post    The readarray builtin  which is a synonym for mapfile  is ideal  It s a builtin command which parses a bytestream into an array variable in one shot  no messing with loops  conditionals  substitutions  or anything else  And it doesn t surreptitiously strip any whitespace from the input string  And  if -O is not given  it conveniently clears the target array before assigning to it  But it s still not perfect  hence my criticism of it as a  wrong answer    First  just to get this out of the way  note that  just like the behavior of read when doing field-parsing  readarray drops the trailing field if it is empty  Again  this is probably not a concern for the OP  but it could be for some use-cases  I ll come back to this in a moment   Second  as before  it does not support multicharacter delimiters  I ll give a fix for this in a moment as well   Third  the solution as written does not parse the OP s input string  and in fact  it cannot be used as-is to parse it  I ll expand on this momentarily as well   For the above reasons  I still consider this to be a  wrong answer  to the OP s question  Below I ll give what I consider to be the right answer     Right answer  Here s a na  ve attempt to make  8 work by just specifying the -d option   string  Paris  France  Europe   readarray -td  a  lt  lt  lt   string   declare -p a     declare -a a   0   Paris   1    France   2     Europe n     We see the result is identical to the result we got from the double-conditional approach of the looping read solution discussed in  7  We can almost solve this with the manual dummy-terminator trick   readarray -td  a  lt  lt  lt   string    declare -p a     declare -a a   0   Paris   1    France   2    Europe   3     n     The problem here is that readarray preserved the trailing field  since the  lt  lt  lt  redirection operator appended the LF to the input string  and therefore the trailing field was not empty  otherwise it would ve been dropped   We can take care of this by explicitly unsetting the final array element after-the-fact   readarray -td  a  lt  lt  lt   string    unset  a -1    declare -p a     declare -a a   0   Paris   1    France   2    Europe     The only two problems that remain  which are actually related  are  1  the extraneous whitespace that needs to be trimmed  and  2  the lack of support for multicharacter delimiters   The whitespace could of course be trimmed afterward  for example  see How to trim whitespace from a Bash variable    But if we can hack a multicharacter delimiter  then that would solve both problems in one shot   Unfortunately  there s no direct way to get a multicharacter delimiter to work  The best solution I ve thought of is to preprocess the input string to replace the multicharacter delimiter with a single-character delimiter that will be guaranteed not to collide with the contents of the input string  The only character that has this guarantee is the NUL byte  This is because  in bash  though not in zsh  incidentally   variables cannot contain the NUL byte  This preprocessing step can be done inline in a process substitution  Here s how to do it using awk   readarray -td    a  lt   lt  awk    gsub        0    print      lt  lt  lt   string      unset  a -1    declare -p a     declare -a a   0   Paris   1   France   2   Europe     There  finally  This solution will not erroneously split fields in the middle  will not cut out prematurely  will not drop empty fields  will not corrupt itself on filename expansions  will not automatically strip leading and trailing whitespace  will not leave a stowaway LF on the end  does not require loops  and does not settle for a single-character delimiter     Trimming solution  Lastly

User · Answer

Here s my hack   Splitting strings by strings is a pretty boring thing to do using bash  What happens is that we have limited approaches that only work in a few cases  split by               and so on  or we have a variety of side effects in the outputs   The approach below has required a number of maneuvers  but I believe it will work for most of our needs      bin bash    --------------------------------------   SPLIT FUNCTION   ----------------  F SPLIT R    f split            It does a  split  into a given string and returns an array       Args          TARGET P  str   Target string to  split           DELIMITER P  Optional str    Delimiter used to  split   If not      informed the split will be done by spaces       Returns          F SPLIT R  array   Array with the provided string separated by the      informed delimiter             F SPLIT R        TARGET P  1     DELIMITER P  2     if   -z   DELIMITER P      then         DELIMITER P         fi      REMOVE N 1     if     DELIMITER P       n      then         REMOVE N 0     fi        NOTE  This was the only parameter that has been a problem so far         By Questor        Ref   https   unix stackexchange com a 390732 61742      if     DELIMITER P              then         DELIMITER P            fi      if     REMOVE N  -eq 1     then            NOTE  Due to bash limitations we have some problems getting the            output of a split by awk inside an array and so we need to use             line break    n  to succeed  Seen this  we remove the line breaks            momentarily afterwards we reintegrate them  The problem is that if            there is a line break in the  string  informed  this line break will            be lost  that is  it is erroneously removed in the output             By Questor         TARGET P   awk  BEGIN  RS  dn    gsub   n    3F2C417D448C46918289218B7337FCAF    printf  0    lt  lt  lt     TARGET P         fi        NOTE  The replace of   n  by  3F2C417D448C46918289218B7337FCAF  results        in more occurrences of  3F2C417D448C46918289218B7337FCAF  than the        amount of   n  that there was originally in the string  one more        occurrence at the end of the string   We can not explain the reason for        this side effect  The line below corrects this problem  By Questor     TARGET P   TARGET P                                        SPLIT NOW   awk -F  DELIMITER P    for i 1  i lt  NF  i    printf   s n    i     lt  lt  lt     TARGET P         while IFS  read -r LINE NOW   do         if     REMOVE N  -eq 1     then                NOTE  We use     to prevent blank lines with no other characters                in the sequence being erroneously removed  We do not know the                reason for this side effect  By Questor             LN NOW WITH N   awk  BEGIN  RS  dn    gsub  3F2C417D448C46918289218B7337FCAF     n    printf  0    lt  lt  lt      LINE NOW                    NOTE  We use the commands below to revert the intervention made                immediately above  By Questor             LN NOW WITH N   LN NOW WITH N                LN NOW WITH N   LN NOW WITH N                 F SPLIT R     LN NOW WITH N           else             F SPLIT R     LINE NOW           fi     done  lt  lt  lt    SPLIT NOW       --------------------------------------   HOW TO USE   ----------------  STRING TO SPLIT      How do I list all databases and tables using psql      sudo -u postgres  usr pgsql-9 4 bin psql -c    l   sudo -u postgres  usr pgsql-9 4 bin psql  lt DB NAME gt  -c    dt           list or  l  list all databases  dt  list all tables in the current database      Ref   https   dba stackexchange com questions 1285 how-do-i-list-all-databases-and-tables-using-psql       f split   STRING TO SPLIT   bin psql -c     --------------------------------------   OUTPUT AND TEST   ----------------  ARR LENGTH    F SPLIT R     for    i 0  i lt       ARR LENGTH -1     i        do     echo    gt  -----------------------------------------      echo    F SPLIT R  i        echo    lt  -----------------------------------------  done  if     STRING TO SPLIT        F SPLIT R 0  bin psql -c  F SPLIT R 1        then     echo    gt  -----------------------------------------      echo  The strings are the same       echo    lt  -----------------------------------------  fi

User · Answer

Another approach can be   str  a  b  c  d     assuming there is a space after     as in Q arr    str          delete all occurrences of       After this  arr  is an array with four strings  This doesn t require dealing IFS or read or any other special stuff hence much simpler and direct

User · Answer

Another way to do it without modifying IFS   read -r -a myarray  lt  lt  lt     string      IFS     Rather than changing IFS to match our desired delimiter  we can replace all occurrences of our desired delimiter      with contents of  IFS via    string      IFS       Maybe this will be slow for very large strings though   This is based on Dennis Williamson s answer

User · Answer

t  one two three  a    echo   t    tr       n    echo    a 2      Prints three

User · Answer

This is similar to the approach by Jmoney38  but using sed   string  1 2 3 4  array   echo  string   sed  s    n g    echo   array 0     Prints 1

User · Answer

The accepted answer works for values in one line  If the variable has several lines   string  first line         second line         third line    We need a very different command to get all lines   while read -r line  do lines     line    done  lt  lt  lt   string   Or the much simpler bash readarray   readarray -t lines  lt  lt  lt   string    Printing all lines is very easy taking advantage of a printf feature   printf   gt   s  n     lines        gt  first line   gt          second line   gt          third line

User · Answer

For multilined elements  why not something like    array    echo -e   a a nb b    tr             amp  amp  array     array              amp  amp  echo    array       INTERELEMENT    a a INTERELEMENT b b INTERELEMENT

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Pure bash multi-character delimiter solution   As others have pointed out in this thread  the OP s question gave an example of a comma delimited string to be parsed into an array  but did not indicate if he she was only interested in comma delimiters  single character delimiters  or multi-character delimiters    Since Google tends to rank this answer at or near the top of search results  I wanted to provide readers with a strong answer to the question of multiple character delimiters  since that is also mentioned in at least one response   If you re in search of a solution to a multi-character delimiter problem  I suggest reviewing Mallikarjun M s post  in particular the response from gniourf gniourf who provides this elegant pure BASH solution using parameter expansion      bin bash str  LearnABCtoABCSplitABCaABCString  delimiter ABC s  str delimiter array     while     s     do     array       s    delimiter            s   s    delimiter    done  declare -p array   Link to cited comment referenced post  Link to cited question  Howto split a string on a multi-character delimiter in bash

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if you use macOS and can t use readarray  you can simply do this- MY STRING  quot string1 string2 string3 quot  array   MY STRING   To iterate over the elements  for element in  quot   array     quot  do     echo  element done

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UPDATE  Don t do this  due to problems with eval   With slightly less ceremony   IFS      eval  array   string     e g   string  foo  bar baz  IFS      eval  array   string   echo   array 1     - gt  bar

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This works for me on OSX   string  1 2 3 4 5  declare -a array   string    If your string has different delimiter  just 1st replace those with space   string  1 2 3 4 5  delimiter     declare -a array    echo  string   tr   delimiter          Simple  -

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Sometimes it happened to me that the method described in the accepted answer didn t work  especially if the separator is a carriage return  In those cases I solved in this way   string  first line second line third line   oldIFS   IFS  IFS     IFS   IFS 0 1    this is useful to format your code with tabs lines    string   IFS   oldIFS   for line in    lines          do         echo  -- gt   line  done

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Since there are so many ways to solve this  let s start by defining what we want to see in our solution    Bash provides a builtin readarray for this purpose  Let s use it  Avoid ugly and unnecessary tricks such as changing IFS  looping  using eval  or adding an extra element then removing it  Find a simple  readable approach that can easily be adapted to similar problems    The readarray command is easiest to use with newlines as the delimiter  With other delimiters it may add an extra element to the array  The cleanest approach is to first adapt our input into a form that works nicely with readarray before passing it in   The input in this example does not have a multicharacter delimiter  If we apply a little common sense  it s best understood as comma separated input for which each element may need to be trimmed  My solution is to split the input by comma into multiple lines  trim each element  and pass it all to readarray   string    Paris France      All of Europe    readarray -t foo  lt   lt  tr       n   lt  lt  lt    string   sed  s         sed  s         declare -p foo    declare -a foo    0   Paris   1   France   2   All of Europe

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Try this  IFS       array  Paris  France  Europe  for item in   array      do echo  item  done   It s simple  If you want  you can also add a declare  and also remove the commas    IFS     declare -a array  Paris France Europe    The IFS is added to undo the above but it works without it in a fresh bash instance

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The key to splitting your string into an array is the multi character delimiter of       Any solution using IFS for multi character delimiters is inherently wrong since IFS is a set of those characters  not a string    If you assign IFS      then the string will break on EITHER     OR     or any combination of them which is not an accurate representation of the two character delimiter of         You can use awk or sed to split the string  with process substitution      bin bash  str  Paris  France  Europe  array    while read -r -d    0  each  do     use a NUL terminated field separator      array     each   done  lt   lt  printf   s    str    awk    gsub             0    print     declare -p array   declare -a array   0   Paris   1   France   2   Europe   output   It is more efficient to use a regex you directly in Bash      bin bash  str  Paris  France  Europe   array    while     str                         do     array      BASH REMATCH 1         capture the field     i    BASH REMATCH                 length of field   delimiter     str   str i                       advance the string by that length done                                  the loop deletes  str  so make a copy if needed  declare -p array   declare -a array   0   Paris   1   France   2   Europe   output      With the second form  there is no sub shell and it will be inherently faster     Edit by bgoldst  Here are some benchmarks comparing my readarray solution to dawg s regex solution  and I also included the read solution for the heck of it  note  I slightly modified the regex solution for greater harmony with my solution   also see my comments below the post       competitors function c readarray   readarray -td    a  lt   lt  awk    gsub        0    print       lt  lt  lt   1      unset  a -1       function c read   a     local REPLY     while read -r -d     do a     REPLY    done  lt   lt  awk    gsub        0    print       lt  lt  lt   1         function c regex   a     local s   1     while     s                   do a      BASH REMATCH 1      s   s    BASH REMATCH    done         helper functions function rep       local -i i -1      for   i   0  i lt  1    i    do         printf  s   2       done        end rep    function testAll       local funcs         local args         local func         local -i rc -1      while      1             do         func   1           if        func        a-zA-Z   a-zA-Z0-9        then             echo  bad function name   func   gt  amp 2              return 2          fi          funcs     func            shift      done      shift      args             for func in    funcs       do         echo -n   func              time  func    args       gt  dev null 2 gt  amp 1    2 gt  amp 1  tr   n               rc   PIPESTATUS 0    if     rc -ne 0     then echo    rc    else echo  fi      done  column -ts         end testAll    function makeStringToSplit       local -i n  1     number of fields     if     n -lt 0     then echo  bad field count   n   gt  amp 2  return 2  fi      if     n -eq 0     then         echo      elif     n -eq 1     then         echo  first field       elif      n  -eq 2     then         echo  first field  last field       else         echo  first field    rep    1-2   mid field    last field       fi        end makeStringToSplit    function testAll splitIntoArray       local -i n  1     number of fields in input string     local s         echo         n field  if     n -ne 1     then echo  s   fi               s    makeStringToSplit   n         testAll c readarray c read c regex     s         end testAll splitIntoArray       results testAll splitIntoArray 1           1 field          c readarray   real  0m0 067s   user 0m0 000s   sys  0m0 000s    c read        real  0m0 064s   user 0m0 000s   sys  0m0 000s    c regex       real  0m0 000s   user 0m0 000s   sys  0m0 000s    testAll splitIntoArray 10           10 fields          c readarray   real  0m0 067s   user 0m0 000s   sys  0m0 000s    c read        real  0m0 064s   user 0m0 000s   sys  0m0 000s    c regex       real  0m0 001s   user 0m0 000s   sys  0m0 000s    testAll splitIntoArray 100           100 fields          c readarray   real  0m0 069s   user 0m0 000s   sys  0m0 062s    c read        real  0m0 065s   user 0m0 000s   sys  0m0 046s    c regex       real  0m0 005s   user 0m0 000s   sys  0m0 000s    testAll splitIntoArray 1000           1000 fields          c readarray   real  0m0 084s   user 0m0 031s   sys  0m0 077s    c read        real  0m0 092s   user 0m0 031s   sys  0m0 046s    c regex       real  0m0 125s   user 0m0 125s   sys  0m0 000s    testAll splitIntoArray 10000           10000 fields          c readarray   real  0m0 209s   user 0m0 093s   sys  0m0 108s    c read        real  0m0 333s   user 0m0 234s   sys  0m0 109s    c regex       real  0m9 095s   user 0m9 078s   sys  0m0 000s    testAll splitIntoArray 100000           100000 fields          c readarray   real  0m1 460s   user 0m0 326s   sys  0m1 124s    c read        real  0m2 780s   user 0m1 686s   sys  0m1 092s    c regex       real  17m38 208s   user 15m16 359s   sys  2m19 375s

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Another way would be   string  Paris  France  Europe  IFS      arr    string     Now your elements are stored in  arr  array   To iterate through the elements   for i in   arr      do echo  i  done

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We can use tr command to split string into the array object  It works both MacOS and Linux       usr bin env bash   currentVersion  1 0 0 140    arrayData    echo  currentVersion   tr       n      len    arrayData       for    i 0  i lt     len-1    i       do         echo  index  i - value   arrayData  i      done   Another option use IFS command  IFS     read -ra arrayData  lt  lt  lt    currentVersion   It is the same as tr arrayData    echo  currentVersion   tr       n      Print the split string for i in    arrayData      do     echo  i done

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I came across this post when looking to parse an input like  word1 word2      none of the above helped me  solved it by using awk  If it helps someone    STRING  value1 value2 value3  array  echo  STRING   awk -F        s    1  for  i   2  i  lt   NF  i    s   s   n  i  print s      for word in   array  do         echo  This is the word  word  done

[arrays] How to split a string into an array in Bash?

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