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Lines 3730-3747
input with a comprehensible error message, not with a crash.
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| 3730 |
@node Dynamic String Input |
3730 |
@node Dynamic String Input |
| 3731 |
@subsection Dynamically Allocating String Conversions |
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@subsection Dynamically Allocating String Conversions |
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3732 |
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| 3733 |
A GNU extension to formatted input lets you safely read a string with no |
3733 |
A GNU and POSIX.1-2008 extension to formatted input lets you safely |
| 3734 |
maximum size. Using this feature, you don't supply a buffer; instead, |
3734 |
read a string with no maximum size. Using this feature, you don't |
| 3735 |
@code{scanf} allocates a buffer big enough to hold the data and gives |
3735 |
supply a buffer; instead, @code{scanf} allocates a buffer big enough |
| 3736 |
you its address. To use this feature, write @samp{a} as a flag |
3736 |
to hold the data and gives you its address. To use this feature, |
| 3737 |
character, as in @samp{%as} or @samp{%a[0-9a-z]}. |
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write @samp{m} as a flag character, as in @samp{%ms} or |
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3738 |
@samp{%m[0-9a-z]}. |
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3739 |
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| 3739 |
The pointer argument you supply for where to store the input should have |
3740 |
The pointer argument you supply for where to store the input should have |
| 3740 |
type @code{char **}. The @code{scanf} function allocates a buffer and |
3741 |
type @code{char **}. The @code{scanf} function allocates a buffer and |
| 3741 |
stores its address in the word that the argument points to. You should |
3742 |
stores its address in the word that the argument points to. You should |
| 3742 |
free the buffer with @code{free} when you no longer need it. |
3743 |
free the buffer with @code{free} when you no longer need it. |
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3744 |
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| 3744 |
Here is an example of using the @samp{a} flag with the @samp{%[@dots{}]} |
3745 |
Here is an example of using the @samp{m} flag with the @samp{%[@dots{}]} |
| 3745 |
conversion specification to read a ``variable assignment'' of the form |
3746 |
conversion specification to read a ``variable assignment'' of the form |
| 3746 |
@samp{@var{variable} = @var{value}}. |
3747 |
@samp{@var{variable} = @var{value}}. |
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3748 |
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Lines 3749-3755
conversion specification to read a ``variable assignment'' of the form
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| 3749 |
@{ |
3750 |
@{ |
| 3750 |
char *variable, *value; |
3751 |
char *variable, *value; |
| 3751 |
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3752 |
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| 3752 |
if (2 > scanf ("%a[a-zA-Z0-9] = %a[^\n]\n", |
3753 |
if (2 > scanf ("%m[a-zA-Z0-9] = %m[^\n]\n", |
| 3753 |
&variable, &value)) |
3754 |
&variable, &value)) |
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@{ |
3755 |
@{ |
| 3755 |
invalid_input_error (); |
3756 |
invalid_input_error (); |
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- |
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