Concatenating strings

Bash:
Concatenating strings

How to:

Here’s the fast track to giving your strings a snug hug in Bash:

# Concatenating by placing strings next to each other
greeting="Hello, "
name="world!"
welcome=$greeting$name
echo $welcome  # Outputs: Hello, world!

# Using curly braces for clarity
version="version"
number=1
full_version=${version}_${number}
echo $full_version  # Outputs: version_1

# Concatenating with variables and literals
timestamp=$(date +%Y%m%d)  # Gets the current date in YYYYMMDD format
filename="backup_${timestamp}.tar.gz"
echo $filename  # Outputs: backup_20230315.tar.gz

Deep Dive

Back in the days before GUIs ruled the land, command lines and scripts were the kings of computer interaction. Concatenating strings has always been essential since it allows for dynamic command and file manipulation.

One historical alternative is the expr command, which feels like a relic now:

older_way=$(expr $greeting $name)

But Bash said, “Who needs that hassle?” and made it natural. How? Well, Bash treats strings like the cozy friends they are: put ’em side by side and they’ll snuggle up together into one long string.

Under the covers, Bash handles this without any special function or syntax for concatenation. The words or variables just flow together. However, if your variables could start with a number or an underscore, you’d usually wrap them in curly braces to prevent confusion with other variable names.

There’s a catch though: spaces matter. If you’re not careful, you might end up with unintended gaps or a squished-together mess.

A current alternative is using the printf function, offering you more control over formatting:

printf -v full_greeting "%s%s" "$greeting" "$name"
echo $full_greeting  # Outputs: Hello, world!

Bash:Concatenating strings

How to:

Deep Dive

See Also

Bash:
Concatenating strings