Check if an element is present in a Bash array

Question

I was wondering if there is an efficient way to check if an element is present within an array  in Bash  I am looking for something similar to what I can do in Python  like   arr     a   b   c   d    if  d  in arr      do your thing else      do something   I ve seen solutions using associative array for bash for Bash 4   but I am wondering if there is another solution out there   Please understand that I know the trivial solution is to iterate in the array  but I don t want that

User · Answer

Obvious caveats aside  if your array was actually like the one above  you could do  if      arr        d    then   do your thing else   do something fi

User · Answer

FWIW  here s what I used   expr    arr             lt  item  gt     This works where there are no delimiters in any of the array items or in the search target  I didn t need to solve the general case for my applicaiton

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1  Initialize array arr and add elements  2  set variable to search for SEARCH STRING  3  check if your array contains element  arr    arr    a   arr    b   arr    c    SEARCH STRING  b   if        arr             SEARCH STRING       then     echo  YES  your arr contains  SEARCH STRING  else     echo  NO  your arr does not contain  SEARCH STRING  fi

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array   word   two words     let s look for  two words    using grep and printf    printf   s n     array        grep -x -q  two words    amp  amp   lt run your if found command here gt    using for    for e in    array       do      e      two words      amp  amp  exit 0  done  exit 1   amp  amp   lt run your if found command here gt    For not found results add     lt run your if notfound command here gt

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Here s another way that might be faster  in terms of compute time  than iterating   Not sure   The idea is to convert the array to a string  truncate it  and get the size of the new array   For example  to find the index of  d    arr  a b c d      temp  echo   arr      temp     temp  d     index    temp       You could turn this into a function like   get-index          Item  1     Array   2          ArgArray      Array        NewArray      Array    Item           Index    NewArray                ArgArray           NewArray         amp  amp  echo -1    echo  Index      You could then call    get-index d arr   and it would echo back 3  which would be assignable with   index  get-index d arr

User · Answer

As bash does not have a built-in value in array operator and the    operator or the       array            item       notation keep confusing me  I usually combine grep with a here-string   colors   black   blue   light green   if grep -q  black   lt  lt  lt     colors      then     echo  match  fi   Beware however that this suffers from the same false positives issue as many of the other answers that occurs when the item to search for is fully contained  but is not equal to another item   if grep -q  green   lt  lt  lt     colors      then     echo  should not match  but does  fi   If that is an issue for your use case  you probably won t get around looping over the array   for color in    colors      do     if      color      green        then         echo  should not match and won t          break     fi done  for color in    colors      do     if      color      light green        then         echo  match          break     fi done

User · Answer

You could do   if        arr             d        then     echo  arr contains d  fi   This will give false positives for example if you look for  a b  -- that substring is in the joined string but not as an array element  This dilemma will occur for whatever delimiter you choose   The safest way is to loop over the array until you find the element   array contains          local seeking  1  shift     local in 1     for element  do         if     element      seeking      then             in 0             break         fi     done     return  in    arr  a b c  d e  f g  array contains  a b     arr       amp  amp  echo yes    echo no      no array contains  d e     arr       amp  amp  echo yes    echo no      yes   Here s a  cleaner  version where you just pass the array name  not all its elements  array contains2           local array   1         local seeking  2     local in 1     for element in     array    do         if     element      seeking      then             in 0             break         fi     done     return  in    array contains2 arr  a b    amp  amp  echo yes    echo no      no array contains2 arr  d e    amp  amp  echo yes    echo no      yes     For associative arrays  there s a very tidy way to test if the array contains a given key  The -v operator    declare -A arr    foo  bar  baz  qux        -v arr foo      amp  amp  echo yes    echo no yes      -v arr bar      amp  amp  echo yes    echo no no   See 6 4 Bash Conditional Expressions in the manual

User · Answer

If array elements don t contain spaces  another  perhaps more readable  solution would be   if echo   arr       grep -q -w  d   then      echo  is in array  else      echo  is not in array  fi

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