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Add advice on printing complex strings (#2446)

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Casey Rodarmor 2024-10-31 16:56:47 -07:00 committed by GitHub
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@ -3583,9 +3583,9 @@ The following command will create two files, `some` and `argument.txt`:
$ just foo "some argument.txt"
```
The users shell will parse `"some argument.txt"` as a single argument, but when
`just` replaces `touch {{argument}}` with `touch some argument.txt`, the quotes
are not preserved, and `touch` will receive two arguments.
The user's shell will parse `"some argument.txt"` as a single argument, but
when `just` replaces `touch {{argument}}` with `touch some argument.txt`, the
quotes are not preserved, and `touch` will receive two arguments.
There are a few ways to avoid this: quoting, positional arguments, and exported
arguments.
@ -3910,6 +3910,38 @@ fetch:
Given the above `justfile`, after running `just fetch`, the recipes in
`foo.just` will be available.
### Printing Complex Strings
`echo` can be used to print strings, but because it processes escape sequences,
like `\n`, and different implementations of `echo` recognize different escape
sequences, using `printf` is often a better choice.
`printf` takes a C-style format string and any number of arguments, which are
interpolated into the format string.
This can be combined with indented, triple quoted strings to emulate shell
heredocs.
Substitution complex strings into recipe bodies with `{…}` can also lead to
trouble as it may be split by the shell into multiple arguments depending on
the presence of whitespace and quotes. Exporting complex strings as environment
variables and referring to them with `"$NAME"`, note the double quotes, can
also help.
Putting all this together, to print a string verbatim to standard output, with
all its various escape sequences and quotes undisturbed:
```just
export FOO := '''
a complicated string with
some dis\tur\bi\ng escape sequences
and "quotes" of 'different' kinds
'''
bar:
printf %s "$FOO"
```
### Alternatives and Prior Art
There is no shortage of command runners! Some more or less similar alternatives