Execute commands and arguments from TSV file

Question

I have a TSV file where each line represents a command and command line arguments. Like this:

ls      ~
cd      /home
cp      dir1    dir2

Each line may have a variable number of columns. Each cell may contain spaces, single quotes and double quotes.

What is a nice way to execute this?

@ShellFish close, but if a cell has spaces in it then they will be treated as separate arguments. I also tried `(IFS=$'\t'; source load.tsv)` — William Entriken, Apr 04 '15 at 01:49
Yea it wasn't an answer just a pointer, hence the comment. Do `sed -i s/ /\\ /g` first. — ShellFish, Apr 04 '15 at 02:22

score 1 · Accepted Answer · edited May 23 '17 at 11:58

Using Bash, read into an array with the IFS set to a tab:

$ cat data
ls      ~
cd      /home
cp      dir1    dir2
al      a b       c  d  
$ vis -t -n data
ls^I~^J
cd^I/home^J
cp^Idir1^Idir2^J
al^Ia b^I  c  d  ^J
$ while IFS=$'\t' read -r -a xyz; do al "${xyz[@]}"; done < data
ls
~
cd
/home
cp
dir1
dir2
al
a b
  c  d  
$ while IFS=$'\t' read -r -a xyz; do al "${xyz[@]}"; done < data | vis -t -n
ls^J
~^J
cd^J
/home^J
cp^J
dir1^J
dir2^J
al^J
a b^J
  c  d  ^J
$

The vis program with options -t -n prints tabs as ^I and newlines as ^J (followed by a newline); the al program prints its arguments one per line — it is effectively equivalent to printf "%s\n" "$@" (it's actually a very simple C program, but the result is the same).

With real commands in the file to be executed, you'd write:

while IFS=$'\t' read -r -a xyz; do "${xyz[@]}"; done < data

On my machine, I got:

$ (while IFS=$'\t' read -r -a xyz; do "${xyz[@]}"; done < data )
ls: ~: No such file or directory
cp: dir1: No such file or directory
a b
  c  d  
$

I used a sub-shell because I didn't want to leave my current directory in my main shell, and I don't have a dir1 to be copied to dir2. Note that the shell did not do tilde-expansion on the results of the parameter expansion, so ls got to see an actual tilde, not the value of my home directory. Fixing the tilde expansion would be painful — excruciatingly painful (see Tilde expansion in quotes). It also means range notation such as {1..10} would not be expanded, and that aliases would not be expanded. See Shell expansions for what would and would not occur.

Actually this does not work if one of the arguments is blank. Also, does not work with zsh — William Entriken, Apr 29 '15 at 15:08
Any sequence of one or more tabs is treated as a single argument separator. You didn't mention `zsh` in the question; the tags are [tag:bash] and [tag:xargs]. Do you know why it doesn't work in `zsh`? If you need empty fields respected, then you certainly have to modify this answer; you probably can't do it with shell and IFS. — Jonathan Leffler, Apr 30 '15 at 01:56

score 0 · Answer 2 · edited Jun 20 '20 at 09:12

Solution:

ruby -ne 'require "shellwords"; system $_.chomp.split("\t").shelljoin'

Proof:

Here is our testing script: cat printArguments.bash:

#!/bin/bash
args=("$@")
for ((i=0; i < $#; i++)) {
   echo "argument $((i+1)): ${args[$i]}"
}

And the test case:

echo $'./printArguments.bash\t1\t\t3' | ruby -ne 'require "shellwords"; system $_.chomp.split("\t").shelljoin'

The result:

argument 1: 1

argument 2:

argument 3: 3

Execute commands and arguments from TSV file

2 Answers2