Category: Linux

If you would like to join an array of elements with a defined delimiter in Bash there is an easy way to go about it by using printf. Following is an example

#!/bin/bash

declare -a arr=()

for i in `seq 1 5`
do
  arr=("${arr[@]}" $i)
done

# Generate a single string joined by a comma.  The printf string can contain
# any arbitrary delimiter.
printf -v joined '%s,' "${arr[@]}"

# Print out the string minus the trailing comma
echo 

The GNU diff command on most Linux and UNIX systems will diff the contents of two files. With Bash, you can, using process substitution, take the output of any arbitrary command and process its input, or output, as a file descriptor. In this way, you can then use diff against the output of two commands as follows

diff <(cmd1) <(cmd2)

Both cmd1 and cmd2 will appear as a file name/file descriptor. The < character indicates that the file descriptor should → Continue reading “Diffing the output of two commands”

Sometimes you will want to ensure that a file is sourced instead of executed. This ensures, among other things, that any environment variables that the script defines remain in your current shell after the script completes.

To do so, use the following to check whether the file was sourced or run in a sub-shell

(return 0 2/dev/null) && sourced=1 || sourced=0
echo "sourced=$sourced"

Bash allows return statements only from functions and in a scripts top level scope IF it → Continue reading “How to check if a file is sourced in Bash”

The TLDR; is to first use tr to replace all occurrences of any horizontal whitespace character with a single space, and then squeeze down any number of spaces to a single space and then define the delimiter for cut as a single space. The following example assumes that you want to see from the 5th column to the end of the line.

<do-something-to-generate-input| tr '[:blank:]' ' ' | tr -s ' ' | cut -d ' ' -f5-

The → Continue reading “Using cut with a delimiter of any amount of whitespace”