How do I “tee” variable number of times in a bash “for loop”?

Question

I understand I can:

ssh archive_server -l user -n "cat text.csv"|tee -a text1.csv|tee -a text2.csv|tee....|tee -a text10.csv

Is there a way to do it aa loop?

for i in `seq 1 10`; do
  echo $i
  tee ???
done

Answer 1

Assuming your shell is really bash (not /bin/sh ), you can build an array (and use a C-style for loop , which unlike the nonstandard external command seq , is guaranteed to be available everywhere bash is):

#!/bin/bash
filenames=( )
for ((i=1; i<=10; i++)); do    # note that the "10" here can be a variable name
  filenames+=( "file$i.txt" )
done
tee -a -- "${filenames[@]}" <text.csv

If you need compatibility with /bin/sh , it gets a little bit more verbose:

#!/bin/sh
tee_between() (
  prefix=$1; suffix=$2; start=$3; end=$4
  set --
  i=$(( $start - 1 )); while [ $(( ( i += 1 ) <= end )) -ne 0 ]; do
    set -- "$@" "file$i.txt"
  done
  exec tee -a -- "$@"
)

tee_between "file" ".txt" 1 10 <text.csv

Note:

• set -- modifies the current process's (or, in this case, the current function's) argument list, using that as an array we can dynamically modify.
• tee_between() ( ) instead of tee_between() { } means that the function runs in a subshell -- a completely separate forked-off process. In consequence of this choice, the exec command will replace only that subshell with a copy of tee , and not the parent process.

Answer 2

You don't need a loop. tee can be given multiple filename arguments, so just give all the output files at once:

cat text.csv | tee -a text{1..10}.csv

If the number of files is dynamic, you can use a loop in $() to insert the filenames into the command line:

cat text.csv | tee -a $(
    for i in $(seq 1 $filecount); do
        echo text$i;
    done)

Just make sure that you don't have any whitespace in the output filename prefix, as the spaces will be treated as argument delimiters.