Trimming strings in BASH

Thu 17 May 2012

I recently needed to trim the last N characters from a string in shell. I wrote this little function to handle the task.
This requires a newer distro that has updated coreutils that includes the 'fold' command (Feb 2010).

#!/bin/bash  
function trimChars() {  
    if [ $2 ]; then  
        TRIM_LAST=$2  
    elif ! [ $2 ]; then  
        TRIM_LAST=4  
    fi  
    if [ $1 ]; then  
        STRING="$1"  
    elif ! [ $1 ]; then  
        STRING="FooBar.xls"  
    fi  
    NEW_STRING=""  
    STRING_ARRAY=(`echo ${STRING} | fold -w1`)  
    NEW_STRLEN=$[ ${#STRING_ARRAY[*]} - ${TRIM_LAST} ]  
    for((i=0;i<${NEW_STRLEN};i++)); do  
        NEW_STRING="${NEW_STRING}${STRING_ARRAY[$i]}"  
    done  
    printf "String in:\t %s\nString out:\t%s\n" ${STRING}
    ${NEW_STRING}  
}  
msnow@host1 ~ $ > trimChars foobarbaz 2  
String in: foobarbaz  
String out: foobarb

Update:
My brother Luke recently found a simpler way of doing this. Always more than 1 way to skin a cat. Some methods are obviously faster. :) Thanks Luke!

msnow@host1 ~ $ > foo=foobarbaz  
msnow@host1 ~ $ > echo ${foo:0:${#foo}-2}  
foobarb

Matt Snow

Trimming strings in BASH