gt Checks if the value of left operand is greater than the value of right

Gt checks if the value of left operand is greater

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-gt Checks if the value of left operand is greater than the value of right operand, if yes then condition becomes true. [ $a -gt $b ] is not true. -lt Checks if the value of left operand is less than the value of right operand, if yes then condition becomes true. [ $a -lt $b ] is true. -ge Checks if the value of left operand is greater than or equal to the value of right operand, if yes then condition becomes true. [ $a -ge $b ] is not true. -le Checks if the value of left operand is less than or equal to the value of right operand, if yes then condition becomes true. [ $a -le $b ] is true. It is very important to note here that all the conditional expressions would be put inside square braces with one spaces around them, for example [ $a -gt $b ] is correct where as [$a -gt $b] is incorrect. Here is an example which uses all the relational operators: #!/bin/sh a = 10 b = 20 if [ $a - eq $b ] then echo "$a -eq $b : a is equal to b" else echo "$a -eq $b: a is not equal to b" fi if [ $a - ne $b ] then echo "$a -ne $b: a is not equal to b" else echo "$a -ne $b : a is equal to b" fi if [ $a - gt $b ] then echo "$a -gt $b: a is greater than b" else echo "$a -gt $b: a is not greater than b" fi if [ $a - lt $b ] then echo "$a -lt $b: a is less than b"
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else echo "$a -lt $b: a is not less than b" fi if [ $a - ge $b ] then echo "$a -ge $b: a is greater or equal to b" else echo "$a -ge $b: a is not greater or equal to b" fi if [ $a - le $b ] then echo "$a -le $b: a is less or equal to b" else echo "$a -le $b: a is not less or equal to b" fi This would produce following result − 10 - eq 20 : a is not equal to b 10 - ne 20 : a is not equal to b 10 - gt 20 : a is not greater than b 10 - lt 20 : a is less than b 10 - ge 20 : a is not greater or equal to b 10 - le 20 : a is less or equal to b 6.7 Boolean Operators Assume variable a=10 and variable b=20 then: Operato r Description Example ! This is logical negation. This inverts a true condition into false and vice versa. [ ! false ] is true. -o This is logical OR. If one of the operands is true then condition would be true. [ $a -lt 20 -o $b -gt 100 ] is true. -a This is logical AND. If both the operands are true then condition would be true otherwise it would be false. [ $a -lt 20 -a $b -gt 100 ] is false. Here is an example which uses all the boolean operators #!/bin/sh a = 10 b = 20 if [ $a != $b ] then echo "$a != $b : a is not equal to b" else echo "$a != $b: a is equal to b"
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fi if [ $a - lt 100 - a $b - gt 15 ] then echo "$a -lt 100 -a $b -gt 15 : returns true" else echo "$a -lt 100 -a $b -gt 15 : returns false" fi if [ $a - lt 100 - o $b - gt 100 ] then echo "$a -lt 100 -o $b -gt 100 : returns true" else echo "$a -lt 100 -o $b -gt 100 : returns false" fi if [ $a - lt 5 - o $b - gt 100 ] then echo "$a -lt 100 -o $b -gt 100 : returns true" else echo "$a -lt 100 -o $b -gt 100 : returns false" fi This would produce following result − 10 != 20 : a is not equal to b 10 - lt 100 - a 20 - gt 15 : returns true 10 - lt 100 - o 20 - gt 100 : returns true 10 - lt 5 - o 20 - gt 100 : returns false 6.8 String Operators Assume variable a holds "abc" and variable b holds "efg" then: Operato r Description Example = Checks if the value of two operands are equal or not, if yes then condition becomes true.
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  • Fall '17
  • Mr Son
  • Shell, relational operator

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