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#!/bin/bash

# trims trailing spaces and tabs from file, using awk utility
function remove_trail() {

[ ! $# -lt 2 ] || { echo "Usage: $FUNCNAME file-to-trim out-file"; return 1; }

    # args
    in="$1"
    out="$2"

    # this check works fine...

    [ -f "$in" ] && return 0 || { echo "File \""$in"\" does not exist."; return 1; }

    # substitute tabs and spaces for nothing on $in arg, then output result to $out
    awk '{ sub(/[ \t]+$/, ""); print }' "$in" >tmp && mv tmp "$out"
    #however, after previous line I don't get my tmp file nor my $out file created.. WHY :O???
    # give user a friendly message
    echo 'Processing done.. Check your '"$out"' file.'
}

this function is defined in .bashrc, so I could use it daily as a kind of builtin.. so when I open shell I type remove_trail file1 file2 to get file2 written from file1+removed_trailing_spaces.
My question is: Why I am not getting tmp and $out files created in my dir?

share|improve this question

2 Answers 2

up vote 2 down vote accepted

The error is in the following line:

[ -f "$in" ] && return 0 || { echo "File \""$in"\" does not exist."; return 1; }

You return from the function if the in parameter to the function is a file. This would explain the absence of the output file.

Perhaps you wanted to say:

[ -f "$in" ] || { echo "File \""$in"\" does not exist."; return 1; }

or

[ ! -f "$in" ] && { echo "File \""$in"\" does not exist."; return 1; }

Moreover, you wouldn't see the temp file as you move it to the output:

mv tmp "$out"
share|improve this answer
    
maaan.. i was starting to pull my hair off, that return 0 was overseen totally. thanks ;) –  branquito Mar 19 at 14:04
    
yes of course for the tmp file, I know that, just thought that something with mv went wrong so I said, tmp or $out. :) –  branquito Mar 19 at 14:07

Just write it as:

trim() { sed 's/[[:blank:]]*$//'; }

And use it as:

trim < file1 > file2

The rest is superfluous.

To prevent the output file being overwritten, you'd do:

trim() (
  set -C
  sed 's/[[:blank:]]*$//' > "$1"
)

and use it as:

trim < file1 file2

(note the absence of >).

You could also let trim open the input file, but you'd lose the ability to do things like:

cmd | trim out-file 
share|improve this answer
    
I marked @devnull answer as a solution, because it gave solution for my script, I know i could use it shortway, but wanted to paractice my bash script skills ;).. But isn't downside of your approach that file2 would be silently overwritten if existed?? –  branquito Mar 19 at 14:18
    
It would also be overwritten with your approach –  Stéphane Chazelas Mar 19 at 14:46
    
yes you are right, i forgot i removed the line where i check for output file.. anyway thanks for your examples, i learned some things, why are you using braces in first case and parenthesis in another, () fires subshell and {} do not, but i don't see why are you using different ones in this example.. –  branquito Mar 19 at 23:06
    
@branquito, to limit the scope of set -C. –  Stéphane Chazelas Mar 19 at 23:12
    
ah ok, i thought of that but wasn't shure. anyway glad to meet you here, i read a lot of your examples going through bash guides (those where they say courtesy of Stephane Chazelas), lot of nice solutions.. ;) –  branquito Mar 19 at 23:15

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