diff options
Diffstat (limited to 'doc/gawk.texi')
| -rw-r--r-- | doc/gawk.texi | 38 |
1 files changed, 18 insertions, 20 deletions
diff --git a/doc/gawk.texi b/doc/gawk.texi index 1d3793eb..a67689fd 100644 --- a/doc/gawk.texi +++ b/doc/gawk.texi @@ -37,13 +37,11 @@ @ifnotdocbook @set BULLET @bullet{} @set MINUS @minus{} -@set NUL @sc{nul} @end ifnotdocbook @ifdocbook @set BULLET @set MINUS -@set NUL NUL @end ifdocbook @set xref-automatic-section-title @@ -5382,10 +5380,10 @@ with @samp{A}. @cindex POSIX @command{awk}, period (@code{.})@comma{} using In strict POSIX mode (@pxref{Options}), -@samp{.} does not match the @value{NUL} +@samp{.} does not match the @sc{nul} character, which is a character with all bits equal to zero. -Otherwise, @value{NUL} is just another character. Other versions of @command{awk} -may not be able to match the @value{NUL} character. +Otherwise, @sc{nul} is just another character. Other versions of @command{awk} +may not be able to match the @sc{nul} character. @cindex @code{[]} (square brackets), regexp operator @cindex square brackets (@code{[]}), regexp operator @@ -6535,7 +6533,7 @@ a value that you know doesn't occur in the input file. This is hard to do in a general way, such that a program always works for arbitrary input files. -You might think that for text files, the @value{NUL} character, which +You might think that for text files, the @sc{nul} character, which consists of a character with all bits equal to zero, is a good value to use for @code{RS} in this case: @@ -6544,23 +6542,23 @@ BEGIN @{ RS = "\0" @} # whole file becomes one record? @end example @cindex differences in @command{awk} and @command{gawk}, strings, storing -@command{gawk} in fact accepts this, and uses the @value{NUL} +@command{gawk} in fact accepts this, and uses the @sc{nul} character for the record separator. This works for certain special files, such as @file{/proc/environ} on -GNU/Linux systems, where the @value{NUL} character is in fact the record separator. +GNU/Linux systems, where the @sc{nul} character is in fact the record separator. However, this usage is @emph{not} portable to most other @command{awk} implementations. @cindex dark corner, strings, storing Almost all other @command{awk} implementations@footnote{At least that we know about.} store strings internally as C-style strings. C strings use the -@value{NUL} character as the string terminator. In effect, this means that +@sc{nul} character as the string terminator. In effect, this means that @samp{RS = "\0"} is the same as @samp{RS = ""}. @value{DARKCORNER} -It happens that recent versions of @command{mawk} can use the @value{NUL} +It happens that recent versions of @command{mawk} can use the @sc{nul} character as a record separator. However, this is a special case: -@command{mawk} does not allow embedded @value{NUL} characters in strings. +@command{mawk} does not allow embedded @sc{nul} characters in strings. (This may change in a future version of @command{mawk}.) @cindex records, treating files as @@ -6586,7 +6584,7 @@ a value that you know doesn't occur in the input file. This is hard to do in a general way, such that a program always works for arbitrary input files. -You might think that for text files, the @value{NUL} character, which +You might think that for text files, the @sc{nul} character, which consists of a character with all bits equal to zero, is a good value to use for @code{RS} in this case: @@ -6595,23 +6593,23 @@ BEGIN @{ RS = "\0" @} # whole file becomes one record? @end example @cindex differences in @command{awk} and @command{gawk}, strings, storing -@command{gawk} in fact accepts this, and uses the @value{NUL} +@command{gawk} in fact accepts this, and uses the @sc{nul} character for the record separator. This works for certain special files, such as @file{/proc/environ} on -GNU/Linux systems, where the @value{NUL} character is in fact the record separator. +GNU/Linux systems, where the @sc{nul} character is in fact the record separator. However, this usage is @emph{not} portable to most other @command{awk} implementations. @cindex dark corner, strings, storing Almost all other @command{awk} implementations@footnote{At least that we know about.} store strings internally as C-style strings. C strings use the -@value{NUL} character as the string terminator. In effect, this means that +@sc{nul} character as the string terminator. In effect, this means that @samp{RS = "\0"} is the same as @samp{RS = ""}. @value{DARKCORNER} -It happens that recent versions of @command{mawk} can use the @value{NUL} +It happens that recent versions of @command{mawk} can use the @sc{nul} character as a record separator. However, this is a special case: -@command{mawk} does not allow embedded @value{NUL} characters in strings. +@command{mawk} does not allow embedded @sc{nul} characters in strings. (This may change in a future version of @command{mawk}.) @cindex records, treating files as @@ -10558,7 +10556,7 @@ double-quotation marks. For example: @cindex strings, length limitations represents the string whose contents are @samp{parrot}. Strings in @command{gawk} can be of any length, and they can contain any of the possible -eight-bit ASCII characters including ASCII @value{NUL} (character code zero). +eight-bit ASCII characters including ASCII @sc{nul} (character code zero). Other @command{awk} implementations may have difficulty with some character codes. @@ -31719,7 +31717,7 @@ and is managed by @command{gawk} from then on. The API defines several simple @code{struct}s that map values as seen from @command{awk}. A value can be a @code{double}, a string, or an array (as in multidimensional arrays, or when creating a new array). -String values maintain both pointer and length since embedded @value{NUL} +String values maintain both pointer and length since embedded @sc{nul} characters are allowed. @quotation NOTE @@ -31851,7 +31849,7 @@ Scalar values in @command{awk} are either numbers or strings. The indicates what is in the @code{union}. Representing numbers is easy---the API uses a C @code{double}. Strings -require more work. Since @command{gawk} allows embedded @value{NUL} bytes +require more work. Since @command{gawk} allows embedded @sc{nul} bytes in string values, a string must be represented as a pair containing a data-pointer and length. This is the @code{awk_string_t} type. |