Read lines from a file into a Bash array

Question

I am trying to read a file containing lines into a Bash array   I have tried the following so far   Attempt1  a      cat  path to filename       Attempt2  index 0 while read line   do     MYARRAY  index    line      index     index 1   done  lt   path to filename   Both attempts only return a one element array containing the first line of the file  What am I doing wrong   I am running bash 4 1 5

User · Answer

The simplest way to read each line of a file into a bash array is this:

IFS=$'\n' read -d '' -r -a lines < /etc/passwd

Now just index in to the array lines to retrieve each line, e.g.

printf "line 1: %s\n" "${lines[0]}"
printf "line 5: %s\n" "${lines[4]}"

# all lines
echo "${lines[@]}"

User · Answer

Latest revision based on comment from BinaryZebra s comment and tested here   The addition of command eval allows for the expression to be kept in the present execution environment while the expressions before are only held for the duration of the eval   Use  IFS that has no spaces tabs  just newlines CR    IFS    r n  GLOBIGNORE     command eval   XYZ    cat  etc passwd      echo    XYZ 5    sync x 5 0 sync  sbin  bin sync   Also note that you may be setting the array just fine but reading it wrong - be sure to use both double-quotes    and braces    as in the example above    Edit   Please note the many warnings about my answer in comments about possible glob expansion  specifically gniourf-gniourf s comments about my prior attempts to work around  With all those warnings in mind I m still leaving this answer here   yes  bash 4 has been out for many years but I recall that some macs only 2 3 years old have pre-4 as default shell   Other notes   Can also follow drizzt s suggestion below and replace a forked subshell cat with      lt  etc passwd    The other option I sometimes use is just set IFS into XIFS  then restore after   See also Sorpigal s answer which does not need to bother with this

User · Answer

bin bash IFS    n  read  -d   -r -a inlines   lt  testinput IFS    n  read  -d   -r -a  outlines  lt  testoutput counter 0 cat testinput   while read line   do     echo       inlines  counter  -  outlines  counter          counter     counter 1   done   OR Do like this counter 0 readarray a  lt  testinput readarray b  lt  testoutput cat testinput   while read myline   do     echo value is       a  counter  -  b  counter         counter     counter 1   done

User · Answer

One alternate way if file contains strings without spaces with 1string each line   fileItemString   cat  filename  tr   n        fileItemArray   fileItemString    Check   Print whole Array     fileItemArray      Length    fileItemArray

User · Answer

Your first attempt was close   Here is the simplistic approach using your idea   file  somefileondisk  lines  cat  file  for line in  lines  do         echo   line  done

User · Answer

The readarray command  also spelled mapfile  was introduced in bash 4 0   readarray -t a  lt   path to filename

[arrays] Read lines from a file into a Bash array

Examples related to arrays

Examples related to bash