CODEWITHSUNDEEP
zshoh-my-zsh
Daebarkee
Daebarkee

Reputation: 683

In zsh for loop, zero-leading number string generation

I have many part-00001, part-00002, ... files.

I want to use this way:

for ((i=0;i<1000;i++)); do <some command> <formatted string with i>; done.

How can I format "part-000xx"-like string with number i in zsh?

Upvotes: 2

Views: 1667

Answers (1)

hchbaw
hchbaw

Reputation: 5339

It could be done with:

  • typeset -Z 5 i (using builtin typeset -Z [N])
  • printf "part-%05d" $i (using builtin printf "%05d" $i)
  • ${(l:5::0:)i} (using parameter expansion flags l:expr::string1:string2:)

like below:

    typeset -Z 5 j
    for ((i=0;i<1000;i++)); do
      # <some command> <formatted string with i>
      j=$i; echo "part-$j" # use $j here for sure the effects of below 2 lines
      echo "$(printf "part-%05d" $i)"
      echo "part-${(l:5::0:)j}"
    done
    # This outputs below:
    # >> part-00000
    # >> part-00000
    # >> part-00000
    # >> part-00001
    # >> part-00001
    # >> part-00001
    # >> ...
    # >> part-00999

Here is the description for each item.

typeset
-Z [N]
Specially handled if set along with the -L flag. Otherwise, similar to -R, except that leading zeros are used for padding instead of blanks if the first non-blank character is a digit. Numeric parameters are specially handled: they are always eligible for padding with zeroes, and the zeroes are inserted at an appropriate place in the output.
-- zshbuiltins(1), typeset, Shell Builtin Commands

printf
Print the arguments according to the format specification. Formatting rules are the same as used in C.
-- zshubuiltins(1), printf, Shell Builtin Commands

l:expr::string1::string2:
Pad the resulting words on the left. Each word will be truncated if required and placed in a field expr characters wide.
The arguments :string1: and :string2: are optional; neither, the first, or both may be given. Note that the same pairs of delimiters must be used for each of the three arguments. The space to the left will be filled with string1 (concatenated as often as needed) or spaces if string1 is not given. If both string1 and string2 are given, string2 is inserted once directly to the left of each word, truncated if necessary, before string1 is used to produce any remaining padding.
-- zshexpn(1), Parameter Expansion Flags

Upvotes: 2

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