How do I iterate through lines in an external file with shell

Question

Possible Duplicate    Looping through the content of a file in Bash        I have one file with a list of names   I need to loop through all names in this file from an external file with a shell script   How can I do that   Example files   scripts names txt  alison barb charlie david   scripts script sh  NAMES     names from names txt file for NAME in  NAMES  do     echo   NAME  done   How can I explode the names txt file into an array in a separate shell script

User · Answer

I know the purists will hate this method  but you can cat the file   NAMES  cat scripts names txt   names from names txt file for NAME in  NAMES  do    echo   NAME  done

User · Answer

This might work for you   cat  lt  lt     gt names txt  gt  alison  gt  barb  gt  charlie  gt  david  gt    OIFS  IFS  IFS    n   NAMES     lt names txt    IFS  OIFS echo    NAMES      alison barb charlie david echo    NAMES 0    alison for NAME in    NAMES      do echo  NAME done alison barb charlie david

User · Answer

cat names txt while read line  do     echo   line   done

User · Answer

You ll be wanting to use the  read  command  while read name do     echo   name  done  lt  names txt   Note that   name  is quoted -- if it s not  it will be split using the characters in  IFS as delimiters  This probably won t be noticed if you re just echoing the variable  but if your file contains a list of file names which you want to copy  those will get broken down by  IFS if the variable is unquoted  which is not what you want or expect   If you want to use Mike Clark s approach  loading into a variable rather than using read   you can do it without the use of cat   NAMES     lt  scripts names txt    names from names txt file for NAME in  NAMES  do     echo   NAME  done   The problem with this is that it loads the whole file into  NAMES  when you read it back out  you can either get the whole file  if quoted  or the file broken down by  IFS  if not quoted  By default  this will give you individual words  not individual lines  So if the name  Mary Jane  appeared on a line  you would get  Mary  and  Jane  as two separate names  Using read will get around this    although you could also change the value of  IFS

User · Answer

One way would be   while read NAME do     echo   NAME  done  lt  names txt   EDIT  Note that the loop gets executed in a sub-shell  so any modified variables will be local  except if you declare them with declare outside the loop   Dennis Williamson is right  Sorry  must have used piped constructs too often and got confused

[bash] How do I iterate through lines in an external file with shell?

Examples related to bash

Examples related to shell