quotestrdup, quoterunestrdup, unquotestrdup, unquoterunestrdup, quotestrfmt, quoterunestrfmt, quotefmtinstall, doquote, needsrcquote – quoted character strings

#include <u.h>
#include <libc.h>

char *quotestrdup(char *s)

Rune *quoterunestrdup(Rune *s)

char *unquotestrdup(char *s)

Rune *unquoterunestrdup(Rune *s)

int quotestrfmt(Fmt*)

int quoterunestrfmt(Fmt*)

void quotefmtinstall(void)

int (*doquote)(int c)

int needsrcquote(int c)

These routines manipulate character strings, either adding or removing quotes as necessary. In the quoted form, the strings are in the style of rc(1), with single quotes surrounding the string. Embedded single quotes are indicated by a doubled single quote. For instance,
Don't worry!

when quoted becomes
'Don''t worry!'

The empty string is represented by two quotes, ''.

The first four functions act as variants of strdup (see strcat(2)). Each returns a freshly allocated copy of the string, created using malloc(2). Quotestrdup returns a quoted copy of s, while unquotestrdup returns a copy of s with the quotes evaluated. The rune versions of these functions do the same for strings (see runestrcat(2)).

The string returned by quotestrdup or quoterunestrdup has the following properties:
1.    If the original string s is empty, the returned string is ''.
2.    If s contains no quotes, blanks, or control characters, the returned string is identical to s.
3.    If s needs quotes to be added, the first character of the returned string will be a quote. For example, hello world becomes 'hello world' not hello' 'world.

The function pointer doquote is nil by default. If it is non–nil, characters are passed to that function to see if they should be quoted. This mechanism allows programs to specify that characters other than blanks, control characters, or quotes be quoted. Regardless of the return value of *doquote, blanks, control characters, and quotes are always quoted. Needsrcquote is provided as a doquote function that flags any character special to rc(1).

Quotestrfmt and quoterunestrfmt are print(2) formatting routines that produce quoted strings as output. They may be installed by hand, but quotefmtinstall installs them under the standard format characters q and Q. (They are not installed automatically.) If the format string includes the alternate format character #, for example %#q, the printed string will always be quoted; otherwise quotes will only be provided if necessary to avoid ambiguity. In <libc.h> there are #pragma statements so the compiler can type–check uses of %q and %Q in print(2) format strings.


rc(1), malloc(2), print(2), strcat(2)