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Bash shell scripting

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Bash – add a number to a variable

By admin on Jan 12, 2016

To add a number to a variable in bash, there are many approaches. Some of these are:

Declare variable as integer

Once a variable is is declared as integer (declare -i), the addition treats it as integer instead of string.

v=1
v+=1
echo "$v"
declare -i v
v=1
v+=1
echo "$v"
11
2
Env: GNU bash, version 4.2.46

Use bash arithmetic expansion

Use $(()) for bash arithmetic expansion.

v=1
#both $v and v are ok in arithmetic expansion
a=$(($v+1))
b=$((v+1))
echo "$a"
echo "$b"
2
2
Env: GNU bash, version 4.2.46

Suggested posts:

  1. Bash – set default value if a variable is empty
  2. Bash – how to check if a variable is set
  3. Bash – append text to a variable
  4. Bash associative array tutorial
  5. Bash – local and global variables
  6. Bash – how to use functions – quick tutorial
  7. Bash – variables in double quotes vs without quotes
  8. How to specify environment variable for a command on Linux
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Posted in Tutorials | Tagged Bash shell scripting, Shell script, Tutorials

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