Loop through an array of strings in Bash

Question

I want to write a script that loops through 15 strings  array possibly   Is that possible   Something like   for databaseName in listOfNames then     Do something end

User · Accepted Answer

You can use it like this      declare an array variable declare -a arr   element1   element2   element3       now loop through the above array for i in    arr      do    echo   i       or do whatever with individual element of the array done    You can access them using echo    arr 0        arr 1    also   Also works for multi-line array declaration  declare -a arr   element1                    element2   element3                   element4

User · Answer

If you are using Korn shell  there is  set -A databaseName    else there is  declare -a databaseName   To write a script working on all shells     set -A databaseName   db1   db2                   declare -a databaseName   db1   db2          now loop  for dbname in    arr      do    echo   dbname     or whatever  done   It should be work on all shells

User · Answer

Implicit array for script or functions   In addition to anubhava s correct answer  If basic syntax for loop is   for var in    arr       do     var     done   there is a special case in bash   When running a script or a function  arguments passed at command lines will be assigned to    array variable  you can access by  1   2   3  and so on   This can be populated  for test  by   set -- arg1 arg2 arg3       A loop over this array could be written simply   for item  do     echo  This is item   item     done   Note that the reserved work in is not present and no array name too   Sample   set -- arg1 arg2 arg3     for item  do     echo  This is item   item     done This is item  arg1  This is item  arg2  This is item  arg3  This is item         Note that this is same than  for item in      do     echo  This is item   item     done   Then into a script      bin bash  for item  do     printf  Doing something with   s   n    item    done   Save this in a script myscript sh  chmod  x myscript sh  then    myscript sh arg1 arg2 arg3     Doing something with  arg1   Doing something with  arg2   Doing something with  arg3   Doing something with          Same in a function   myfunc     for item do cat  lt  lt  lt  Working about   item     done       Then  myfunc item1 tiem2 time3 Working about  item1   Working about  tiem2   Working about  time3

User · Answer

Try this  It is working and tested   for k in    array      do     echo  k done    For accessing with the echo command  echo   array 0      array 1

User · Answer

What I really needed for this was something like this   for i in   the array   do something  done   For instance   for i in   ps -aux   grep vlc    awk    print  2      do kill -9  i  done    Would kill all processes with vlc in their name

User · Answer

This is also easy to read   FilePath         tmp path1       FilePath 0        tmp path2       FilePath 1      Loop for Path in    FilePath      do     echo   Path  done

User · Answer

That is possible  of course   for databaseName in a b c d e f  do     do something like  echo  databaseName done    See Bash Loops for  while and until for details

User · Answer

Possible first line of every Bash script session   say     for line in          do printf   s n     line     done       Use e g      aa   7 -4 -e     say    aa      7 -4 -e   May consider  echo interprets -e as option here

User · Answer

Single line looping    declare -a listOfNames   db a   db b   db c    for databaseName in   listOfNames      do echo  databaseName  done    you will get an output like this   db a db b db c

User · Answer

The declare array doesn t work for Korn shell  Use the below example for the Korn shell   promote sla chk lst  cdi xlob   set -A promote arry  promote sla chk lst  for i in   promote arry          do             echo  i     done

User · Answer

This is similar to user2533809 s answer  but each file will be executed as a separate command      bin bash names  RA RB R C RD   while read -r line  do     echo line    line  done  lt  lt  lt    names

User · Answer

Yes for Item in Item1 Item2 Item3 Item4     do     echo  Item   done  Output  Item1 Item2 Item3 Item4  To preserve spaces  single or double quote list entries and double quote list expansions  for Item in  Item 1   Item 2   Item 3   Item 4      do     echo  quot  Item quot    done  Output  Item 1 Item 2 Item 3 Item 4  To make list over multiple lines for Item in Item1               Item2               Item3               Item4   do     echo  Item   done  Output  Item1 Item2 Item3 Item4   Simple list variable List   Item1 Item2 Item3    or List         Item1        Item2        Item3         Display the list variable  echo   List      Output  Item1 Item2 Item3  Loop through the list  for Item in   List        do     echo  Item    done  Output  Item1 Item2 Item3  Create a function to go through a list  Loop      for item in             do        echo   item       done   Loop   List      Using the declare keyword  command  to create the list  which is technically called an array  declare -a List                     quot element 1 quot                     quot element 2 quot                     quot element 3 quot                    for entry in  quot   List     quot     do      echo  quot  entry quot     done  Output  element 1 element 2 element 3  Creating an associative array  A dictionary  declare -A continent  continent Vietnam  Asia continent France  Europe continent Argentina  America  for item in  quot    continent     quot      do     printf  quot  item is in   continent  item    n quot    done  Output   Argentina is in America  Vietnam is in Asia  France is in Europe  CSV variables or files in to a list   Changing the internal field separator from a space  to what ever you want   In the example below it is changed to a comma List  quot Item 1 Item 2 Item 3 quot  Backup of internal field separator  IFS IFS   for item in  List     do     echo  item   done IFS  Backup of internal field separator  Output  Item 1 Item 2 Item 3  If need to number them      this is called a back tick  Put the command inside back ticks   command    It is next to the number one on your keyboard and or above the tab key  on a standard American English language keyboard  List    Start count 0 Step count 0 1 Stop count 1 for Item in  seq  Start count  Step count  Stop count      do         List   Item  Item      done for Item in   List         do          echo  Item     done  Output is  Item 0 0 Item 0 1 Item 0 2 Item 0 3 Item 0 4 Item 0 5 Item 0 6 Item 0 7 Item 0 8 Item 0 9 Item 1 0  Becoming more familiar with bashes behavior  Create a list in a file cat  lt  lt EOF gt  List entries txt Item1 Item 2   Item 3   quot Item 4 quot  Item 7      quot Item 6      quot   quot Item 6     quot  Item 8    PWD  Item 8    PWD   quot Item 9    PWD quot  EOF  Read the list file in to a list and display List   cat List entries txt  echo  List echo   List  echo  quot  List quot  echo   List     echo    List      echo  quot   List     quot  echo   List     echo    List      echo  quot   List     quot   BASH commandline reference manual   Special meaning of certain characters or words to the shell

User · Answer

None of those answers include a counter        bin bash    declare an array variable declare -a array   one   two   three      get length of an array arraylength    array        use for loop to read all values and indexes for    i 1  i lt   arraylength  1  i       do   echo  i         arraylength          array  i-1   done   Output   1     3     one 2     3     two 3     3     three

User · Answer

Simple way    arr   sharlock    bomkesh    feluda       declare array  len    arr        it returns the array length   iterate with while loop i 0 while    i -lt  len   do     echo   arr  i       i    i 1   done    iterate with for loop for i in  arr do   echo  i done   iterate with splice  echo   arr    0 3

User · Answer

How you loop through an array  depends on the presence of new line characters  With new line characters separating the array elements  the array can be referred to as  quot  array quot   otherwise it should be referred to as  quot   array     quot   The following script will make it clear     bin bash  mkdir temp mkdir temp aaa mkdir temp bbb mkdir temp ccc array   ls temp  array1  aaa bbb ccc  array2   echo -e  quot aaa nbbb nccc quot    echo   array  echo  quot  array quot  echo for dirname in  quot  array quot   do     echo  quot  dirname quot  done echo for dirname in  quot   array     quot   do     echo  quot  dirname quot  done echo echo   array1  echo  quot  array1 quot  echo for dirname in  quot  array1 quot   do     echo  quot  dirname quot  done echo for dirname in  quot   array1     quot   do     echo  quot  dirname quot  done echo echo   array2  echo  quot  array2 quot  echo for dirname in  quot  array2 quot   do     echo  quot  dirname quot  done echo for dirname in  quot   array2     quot   do     echo  quot  dirname quot  done rmdir temp aaa rmdir temp bbb rmdir temp ccc rmdir temp

User · Answer

Surprised that nobody s posted this yet -- if you need the indices of the elements while you re looping through the array  you can do this   arr  foo bar baz   for i in    arr     do     echo  i    arr i    done   Output   0 foo 1 bar 2 baz   I find this a lot more elegant than the  traditional  for-loop style  for    i 0  i lt    arr      i             arr     and  i don t need to be quoted because they re just numbers  some would suggest quoting them anyway  but that s just personal preference

User · Answer

listOfNames  db one db two db three  for databaseName in  listOfNames do   echo  databaseName done   or just  for databaseName in db one db two db three do   echo  databaseName done

User · Answer

I loop through an array of my projects for a git pull update      bin sh projects   web ios android   for project in  projects do     cd   HOME develop  project  amp  amp  git pull end

User · Answer

In the same spirit as 4ndrew s answer   listOfNames  RA RB R C RD     To allow for other whitespace in the string    1  add double quotes around the list variable  or   2  see the IFS note  under  Side Notes    for databaseName in   listOfNames        lt -- Note  Added    quotes  do   echo   databaseName      i e  do action   processing of  databaseName here     done    Outputs   RA   RB   R C   RD   B  No whitespace in the names   listOfNames  RA RB R C RD   for databaseName in  listOfNames    Note  No quotes do   echo   databaseName      i e  do action   processing of  databaseName here     done    Outputs   RA   RB   R   C   RD   Notes   In the second example  using listOfNames  RA RB R C RD  has the same output    Other ways to bring in data include     stdin  listed below    variables   an array  the accepted answer    a file      Read from stdin    line delimited  each databaseName is stored on a line  while read databaseName do   echo   databaseName     i e  do action   processing of  databaseName here    done    lt  lt  lt  or another input method here    the bash IFS  field separator to line   1  delimiter can be specified in the script to allow other whitespace  i e  IFS   n   or for MacOS IFS   r   I like the accepted answer also    -- I ve include these snippets as other helpful ways that also answer the question  Including    bin bash at the top of the script file indicates the execution environment  It took me months to figure out how to code this simply      Other Sources  while read loop

User · Answer

You can use the syntax of   arrayName         bin bash   declare an array called files  that contains 3 values files     etc passwd    etc group    etc hosts    for i in    files      do     echo   i  done

[arrays] Loop through an array of strings in Bash?

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