bash script - loop function

Question

I managed to write the following script:

#!/bin/bash #files list file1=/tmp/1wall_long.txt file2=/tmp/1wall_test1.txt file3=/tmp/1wall_test2.txt file4=/tmp/1wall_test3.txt file5=/tmp/3mt_long.txt file6=/tmp/3mt_OpenSpace_test1.txt file7=/tmp/3mt_OpenSpace_test2.txt file8=/tmp/3mt_OpenSpace_test3.txt file9=/tmp/3rooms_test1.txt file10=/tmp/3rooms_test2.txt file11=/tmp/3rooms_test3.txt file12=/tmp/20mt_OpenSpace_test1.txt file13=/tmp/20mt_OpenSpace_test2.txt file14=/tmp/20mt_OpenSpace_test3.txt #script for 1wall_long file if [ ! -e "$file1" ]; then #check if the file exist echo "File 1wall_long.txt does not exist" #if not exist print echo output else sed -i -e 's/- /-/g' $file1 #remove space on the first 10 values awk '{print $7}' $file1 > /tmp/1wall_long_S.txt #print the column number 7 and copy the output in a file rm $file1 #remove old file fi 

The script is repeated for all files described in the variable (basically I have the same script repeated 14 times with different variables) Is there a better way to do it and what is the best practice in these situations ?

Answer 1

loopless

first use a function

function sevenc { if [ ! -e "$1" ]; then #check if the file exist echo "File $1 does not exist" #if not exist print echo output else sed -i -e 's/- /-/g' "$1" #remove space on the first 10 values awk '{print $7}' "$1" > /tmp/$(basename $1.txt)_S.txt #print the column number 7 and copy the output in a file rm "$1" #remove old file fi } 

• when the shell recognize a function, it will pass argument (if any to $1 $2 ... and so on).
• by the way

's/- /-/g' "$1" #remove space on the first 10 values

NO, it turn all space- to - on the line, be there 1, 4, 10 or 255.

then no need for more var

sevenc /tmp/1wall_long.txt sevenc /tmp/1wall_test1.txt sevenc /tmp/1wall_test2.txt sevenc /tmp/1wall_test3.txt sevenc /tmp/3mt_long.txt sevenc /tmp/3mt_OpenSpace_test1.txt sevenc /tmp/3mt_OpenSpace_test2.txt sevenc /tmp/3mt_OpenSpace_test3.txt sevenc /tmp/3rooms_test1.txt sevenc /tmp/3rooms_test2.txt sevenc /tmp/3rooms_test3.txt sevenc /tmp/20mt_OpenSpace_test1.txt sevenc /tmp/20mt_OpenSpace_test2.txt sevenc /tmp/20mt_OpenSpace_test3.txt 

(provided you have no more use of fileXX var).

loopless (sol. 2)

should you want to pass more argument, and using Terdon's optimisation try

function eight { file=$1 destdir=${2-/tmp} # use second arg if defined, else /tmp exten=${3-S} if [ ! -e "$file" ]; then #check if the file exist echo "File $file does not exist" #if not exist print echo output else sed -e 's/- /-/g' "$file" \ awk '{print $7}' "$1" > /"$destdir"/$(basename $1.txt)_"$exten".txt #print the column number 7 and copy the output in a file rm "$file" #remove old file fi } 

to be called with

eight /tmp/1wall_test3.txt /my/projec/dir T ## will use /my/project/dir as dit, T as extension eight /tmp/1wall_test1.txt /my/project ## will use /my/project as dir eignt /tmp/1wall_test2.txt ## will use default value 

those function can be defined in .bashrc and be use interactively.

with loop

while read f do if [ ! -e "$f" ]; then #check if the file exist echo "File $1 does not exist" #if not exist print echo output else sed -i -e 's/- /-/g' "$f" #remove space on the first 10 values awk '{print $7}' "$f" > "/tmp/$(basename $f .txt)_S.txt" #print the column number 7 and copy the output in a file rm "$f" #remove old file fi done <<EOF /tmp/1wall_long.txt /tmp/1wall_test1.txt /tmp/1wall_test2.txt /tmp/1wall_test3.txt /tmp/3mt_long.txt /tmp/3mt_OpenSpace_test1.txt /tmp/3mt_OpenSpace_test2.txt /tmp/3mt_OpenSpace_test3.txt /tmp/3rooms_test1.txt /tmp/3rooms_test2.txt /tmp/3rooms_test3.txt /tmp/20mt_OpenSpace_test1.txt /tmp/20mt_OpenSpace_test2.txt /tmp/20mt_OpenSpace_test3.txt EOF 

Answer 2

Personally, I would avoid hardcoding the file names. That is rarely a good idea and it is usually better to have the option of passing target files as arguments. Additionally, you are modifying the file in place and then deleting the original. That's not efficient, just modify the file on the fly and print the 7th column without having to write it to disk. For example:

#!/usr/bin/env bash ## Iterate over the file names given for file in "$@"; do ## Get the output file's name. The ${file%.*} is ## the file's anme without its extension. outfile="${file%.*}"_S.txt ## If the file exists if [ -e "$file" ]; then ## remove the spaces and print the 7th column sed 's/- /-/g' "$file" | awk '{print $7}' > "$outfile" && ## Delete the original but only if the step ## above was successful (that's what the && does)/ rm "$file" else ## If the file doesn't exist, print an error message echo "The file $file does not exist!" fi done 

Then, you can run the script like this:

foo.sh /tmp/1wall_long.txt /tmp/1wall_test1.txt /tmp/1wall_test2.txt /tmp/1wall_test3.txt /tmp/20mt_OpenSpace_test1.txt /tmp/20mt_OpenSpace_test2.txt /tmp/20mt_OpenSpace_test3.txt /tmp/3mt_long.txt /tmp/3mt_OpenSpace_test1.txt /tmp/3mt_OpenSpace_test2.txt /tmp/3mt_OpenSpace_test3.txt /tmp/3rooms_test1.txt /tmp/3rooms_test2.txt /tmp/3rooms_test3.txt 

If you do want to have the names hard coded, just use an array as suggested by @choroba:

#!/usr/bin/env bash files=(/tmp/1wall_long.txt /tmp/1wall_test1.txt /tmp/1wall_test2.txt /tmp/1wall_test3.txt /tmp/20mt_OpenSpace_test1.txt /tmp/20mt_OpenSpace_test2.txt /tmp/20mt_OpenSpace_test3.txt /tmp/3mt_long.txt /tmp/3mt_OpenSpace_test1.txt /tmp/3mt_OpenSpace_test2.txt /tmp/3mt_OpenSpace_test3.txt /tmp/3rooms_test1.txt /tmp/3rooms_test2.txt /tmp/3rooms_test3.txt ) ## Iterate over the file names given for file in "${files[@]}"; do ## Get the output file's name. The ${file%.*} is ## the file's anme without its extension. outfile="${file%.*}"_S.txt ## If the file exists if [ -e "$file" ]; then ## remove the spaces and print the 7th column sed 's/- /-/g' "$file" | awk '{print $7}' > "$outfile" && ## Delete the original but only if the step ## above was successful (that's what the && does)/ rm "$file" else ## If the file doesn't exist, print an error message echo "The file $file does not exist!" fi done 

Answer 3

You can use an array of files and loop over it with for:

#!/bin/bash files=(/tmp/1wall_long.txt /tmp/1wall_test1.txt /tmp/1wall_test2.txt /tmp/1wall_test3.txt /tmp/3mt_long.txt /tmp/3mt_OpenSpace_test1.txt /tmp/3mt_OpenSpace_test2.txt /tmp/3mt_OpenSpace_test3.txt /tmp/3rooms_test1.txt /tmp/3rooms_test2.txt /tmp/3rooms_test3.txt /tmp/20mt_OpenSpace_test1.txt /tmp/20mt_OpenSpace_test2.txt /tmp/20mt_OpenSpace_test3.txt ) for file in "${files[@]}" ; do if [ ! -e "$file" ]; then echo "File $file does not exist" else sed -i -e 's/- /-/g' "$file" # Use parameter expansion to create the new file name. newfile=${file%.txt}_S.txt awk '{print $7}' "$file" > "$newfile" rm "$file" fi done