Conditional block vs conditional statement (if) Say I have a file: PRO 1 GLN 5.55112e-17 ILE -6.245e-17 THR 5.55112e-17 I want every line that has a number unequal to 1 in the second column to change it to 0 and keep the rest. If I use `if` (i.e conditional statement), everything is OK: awk '{if($2!=1){print $1,"0"}else{print $0}}' file PRO 1 GLN 0 ILE 0 THR 0 But when I use the conditional block, something undesired happens: awk '$2!=1 {print $1,"0"} {print $0}' file PRO 1 GLN 0 GLN 5.55112e-17 ILE 0 ILE -6.245e-17 THR 0 THR 5.55112e-17 You can see what's wrong. * How do I fix this error? * Why does this error occur? * What's the different between a conditional statement and a conditional block?

In an `if` statement, you have an `else`. If `if` doesn't match, the `else` branch is executed.

In a conditional statement, both actions are executed, regardless of the condition is true or false.

A simple fix:


$ awk '$2!=1 {print $1,"0";next};{print $0}' file
PRO 1
GLN 0
ILE 0
THR 0


And you can make it more concise:


$ awk '$2 != 1 {print $1,"0";next};1' file
PRO 1
GLN 0
ILE 0
THR 0


When condition is true `1` and there is no action, `awk` default behavior is `print`. `print` with no argument will print `$0` by default.