Return to Answer

This works too:

$ rename -n 'BEGIN {our $i = 28}; s/_.*/sprintf("_%03d.png", our $i++)/e' *.png 

Note: you do not have to declare the variable with our every time you use the variable. Declare it only once in each code block, i.e. once in BEGIN and once in the main script - either before it is first used in a code block, or when it is first used in a block.

Note: you do not have to declare the variable with our every time you use the variable. Declare it only once in each code block, i.e. once in BEGIN and once in the main script - either before it is first used in a code block, or when it is first used in a block. i.e. this works too:

$ rename -n 'BEGIN {our $i = 28}; s/_.*/sprintf("_%03d.png", our $i++)/e' *.png 

One more thing:

Declaring $i as a state variable (see perldoc -f state) works too, without needing a BEGIN block but I would recommend avoiding it unless you have a really good grasp of variable scope in perl:

$ rename -n 'state $i = 28; s/_.*/sprintf("_%03d.png", $i++)/e' *.png rename(abc_128390.png, abc_028.png) rename(abc_138493.png, abc_029.png) rename(abc_159084.png, abc_030.png) 

See Persistent Private Variables and Coping with Scoping (which doesn't even mention state because it was written in 1998 before perl v5.10 when state was introduced, but is still good reading to understand perl variable scope)

As you've already discovered, putting our $i = 28; in the main script doesn't work because it resets $i to 28 for every filename - rename executes every statement in the main script once for every filename.

You can set an initial value for a variable (or run any other setup statements that only needs to be done once per script) in a BEGIN block (e.g. BEGIN {our $i = 28};, which is only executed once when the script first executes.

You still have to declare the variable as a package global variable with our in both the BEGIN block and the main script because rename runs perl code in strict mode. See perldoc -f our and perldoc strict.

$ rename -n 'BEGIN {our $i = 28}; our $i; s/_.*/sprintf("_%03d.png", $i++)/e' *.png rename(abc_128390.png, abc_028.png) rename(abc_138493.png, abc_029.png) rename(abc_159084.png, abc_030.png) 

This works too:

$ rename -n 'BEGIN {our $i = 28}; s/_.*/sprintf("_%03d.png", our $i++)/e' *.png 

Note: you do not have to declare the variable with our every time you use the variable. Declare it only once in each code block, i.e. once in BEGIN and once in the main script - either before it is first used, or when it is first used.

Also worth noting: if you need to use a variable that gets reset for every filename, declare it as a local variable with my rather than our. See perldoc -f my.

For a contrived example:

$ rename -n 'BEGIN {our $i = 28}; our $i; my $formatted_number = sprintf("_%03d.png", $i++); s/_.*/$formatted_number/' *.png rename(abc_128390.png, abc_028.png) rename(abc_138493.png, abc_029.png) rename(abc_159084.png, abc_030.png) 

In this version, we don't need the /e modifier to the s/// operation because we don't need to evaluate the replacement as perl code, just use it as an interpolated variable. See perldoc -f s

As you've already discovered, putting our $i = 28; in the main script doesn't work because it resets $i to 28 for every filename - rename executes every statement in the main script once for every filename.

You can set an initial value for a variable (or any other setup code that only needs to be run once when the script first executes) in a BEGIN block - e.g. BEGIN {our $i = 28};.

You still have to declare the variable as a package global variable with our in both the BEGIN block and the main script because rename runs perl code in strict mode. See perldoc -f our and perldoc strict.

$ rename -n 'BEGIN {our $i = 28}; our $i; s/_.*/sprintf("_%03d.png", $i++)/e' *.png rename(abc_128390.png, abc_028.png) rename(abc_138493.png, abc_029.png) rename(abc_159084.png, abc_030.png) 

This works too:

$ rename -n 'BEGIN {our $i = 28}; s/_.*/sprintf("_%03d.png", our $i++)/e' *.png 

Note: you do not have to declare the variable with our every time you use the variable. Declare it only once in each code block, i.e. once in BEGIN and once in the main script - either before it is first used in a code block, or when it is first used in a block.

Also worth noting: if you need to use a variable that should be reset for every filename, declare it as a local variable with my rather than our. See perldoc -f my.

For a contrived example:

$ rename -n 'BEGIN {our $i = 28}; our $i; my $formatted_number = sprintf("_%03d.png", $i++); s/_.*/$formatted_number/' *.png rename(abc_128390.png, abc_028.png) rename(abc_138493.png, abc_029.png) rename(abc_159084.png, abc_030.png) 

In this version, we don't need the /e modifier to the s/// operation because we don't need to evaluate the replacement as perl code, just use it as an interpolated variable. See perldoc -f s