Methods for variable auto-increment in Linuxshell (or calculation)

Several methods (or calculation operations) for variable auto-increment in Linuxshell-Linux general technology-Linux technology and application information. For more information, see the following. I remember the section about the Linux shell loop that involved variable auto-increment (integer arithmetic operation). I think it is easy to make a mistake. Now I will summarize several common methods:
1. Use expr
# Expr 10 + 10 ==> 20
# A = 'expr 10% 3'; echo $ a ==> 1
# B = 10; B = 'expr $ B + 1' => 11 (implement variable auto-increment 1)
2. Use $ []
# Echo $[10 + 10] ==> 20
# A = $ [10% 1]; echo a => 1
# B = 10; B = $ [$ B + 1]; echo B => 11 (implement variable auto-increment 1)

The auto-increment operation of variables can also be implemented as follows:
# C = 100
# Let c + = 1 ==> 101

If it is helpful to you, please reply to the support! Thank you.
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[ This post was last edited by lyq617617]