How do I use the lines of a file as arguments of a command

Question

Say  I have a file foo txt specifying N arguments  arg1 arg2     argN   which I need to pass to the command my command  How do I use the lines of a file as arguments of a command

User · Answer

I suggest using  command   echo   tr   n       lt  parameters cfg    Simply trim the end-line characters and replace them with spaces  and then push the resulting string as possible separate arguments with echo

User · Answer

After editing  Wesley Rice s answer a couple times  I decided my changes were just getting too big to continue changing his answer instead of writing my own  So  I decided I need to write my own   Read each line of a file in and operate on it line-by-line like this      bin bash input   path to txt file  while IFS  read -r line do   echo   line  done  lt    input    This comes directly from author Vivek Gite here  https   www cyberciti biz faq unix-howto-read-line-by-line-from-file   He gets the credit       Syntax  Read file line by line on a Bash Unix  amp  Linux shell    1  The syntax is as follows for bash  ksh  zsh  and all other shells to read a file line by line   2  while read -r line  do COMMAND  done  lt  input file   3  The -r option passed to read command prevents backslash escapes from being interpreted    4  Add IFS  option before read command to prevent leading trailing whitespace from being trimmed -   5  while IFS  read -r line  do COMMAND on  line  done  lt  input file       And now to answer this now-closed question which I also had  Is it possible to  git add  a list of files from a file  - here s my answer   Note that FILES STAGED is a variable containing the absolute path to a file which contains a bunch of lines where each line is a relative path to a file I d like to do git add on  This code snippet is about to become part of the  eRCaGuy dotfiles useful scripts sync git repo to build machine sh  file in this project  to enable easy syncing of files in development from one PC  ex  a computer I code on  to another  ex  a more powerful computer I build on   https   github com ElectricRCAircraftGuy eRCaGuy dotfiles   while IFS  read -r line do     echo    git add    line        git add   line   done  lt    FILES STAGED    References    Where I copied my answer from  https   www cyberciti biz faq unix-howto-read-line-by-line-from-file  For loop syntax  https   www cyberciti biz faq bash-for-loop    Related    How to read contents of file line-by-line and do git add on it  Is it possible to  git add  a list of files from a file

User · Answer

Here s how I pass contents of a file as an argument to a command     foo --bar    cat   bar txt

User · Answer

If all you need to do is to turn file arguments txt with contents  arg1 arg2 argN   into my command arg1 arg2 argN then you can simply use xargs   xargs -a arguments txt my command   You can put additional static arguments in the xargs call  like xargs -a arguments txt my command staticArg which will call my command staticArg arg1 arg2 argN

User · Answer

command   lt  file    will pass file contents to the command on stdin  but will strip newlines  meaning you couldn t iterate over each line individually  For that you could write a script with a  for  loop   for line in  cat input file   do some command   line   done   Or  the multi-line variant    for line in  cat input file  do     some command   line  done   Or  multi-line variant with     instead of       for line in   cat input file  do     some command   line  done   References    For loop syntax  https   www cyberciti biz faq bash-for-loop

User · Answer

In my bash shell the following worked like a charm   cat input file   xargs -I   sh -c  command1    command2    command3       where input file is  arg1 arg2 arg3   As evident  this allows you to execute multiple commands with each line from input file  a nice little trick I learned here

User · Answer

As already mentioned  you can use the backticks or   cat filename    What was not mentioned  and I think is important to note  is that you must remember that the shell will break apart the contents of that file according to whitespace  giving each  word  it finds to your command as an argument  And while you may be able to enclose a command-line argument in quotes so that it can contain whitespace  escape sequences  etc   reading from the file will not do the same thing  For example  if your file contains   a  b c  d   the arguments you will get are   a  b c  d   If you want to pull each line as an argument  use the while read do construct   while read i   do command name  i   done  lt  filename

User · Answer

If your shell is bash  amongst others   a shortcut for   cat afile  is    lt  afile   so you d write   mycommand     lt  file txt     Documented in the bash man page in the  Command Substitution  section   Alterately  have your command read from stdin  so  mycommand  lt  file txt

User · Answer

You do that using backticks   echo World  gt  file txt echo Hello  cat file txt

User · Answer

None of the answers seemed to work for me or were too complicated  Luckily  it s not complicated with xargs  Tested on Ubuntu 20 04   This works with each arg on a separate line in the file as the OP mentions and was what I needed as well  cat foo txt   xargs my command  One thing to note is that it doesn t seem to work with aliased commands  The accepted answer works if the command accepts multiple args wrapped in a string  In my case using  Neo Vim it does not and the args are all stuck together  xargs does it probably and actually gives you separate arguments supplied to the command

User · Answer

If you want to do this in a robust way that works for every possible command line argument  values with spaces  values with newlines  values with literal quote characters  non-printable values  values with glob characters  etc   it gets a bit more interesting     To write to a file  given an array of arguments   printf   s 0     arguments       gt file      replace with  argument one    argument two   etc  as appropriate     To read from that file and use its contents  in bash  ksh93  or another recent shell with arrays    declare -a args    while IFS    read -r -d    item  do   args      item    done  lt file run your command    args          To read from that file and use its contents  in a shell without arrays  note that this will overwrite your local command-line argument list  and is thus best done inside of a function  such that you re overwriting the function s arguments and not the global list    set -- while IFS    read -r -d    item  do   set --        item  done  lt file run your command        Note that -d  allowing a different end-of-line delimiter to be used  is a non-POSIX extension  and a shell without arrays may also not support it  Should that be the case  you may need to use a non-shell language to transform the NUL-delimited content into an eval-safe form   quoted list          Works with either Python 2 x or 3 x   python -c   import sys  pipes  shlex quote   pipes quote if hasattr pipes   quote   else shlex quote print     join  quote s  for s in sys stdin read   split   0     -1           eval  set --   quoted list  lt file   run your command

[linux] How do I use the lines of a file as arguments of a command?

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