On 25/11/15 11:17, Pádraig Brady wrote:
> On 25/11/15 09:51, John Summerfield wrote:
>> Here, and possibly other places, you say that the following command
>> eliminates duplicate blank lines.
>> tr -s '\n'
>>
>> This is in the --group discussion.
>>
>> What happens is that it removes all blank lines (two or more NL characters).
>
> True. That is confusing.
> I also notice that the docs for tr -s aren't accurate.
>
> patch coming up...
attached
>From c1906ff06f394dc71f3764174c7c7002765c948e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C3=A1draig=20Brady?= <p...@draigbrady.com>
Date: Wed, 25 Nov 2015 11:57:34 +0000
Subject: [PATCH] doc: clarify descriptions for tr --squeeze-repeats
* doc/coreutils.texi (uniq invocation): Fix the description of
problematic input to say "blank lines" rather than "two or more
blank lines".
(tr invocation): Clarify that -s only works with SET1 when
not translating (when SET2 not specified). Also explitly
state in examples where blank lines are deleted.
Also add "deleting" to the menu item.
* src/tr.c (usage): Improve the -s summary to say it always
operates on the last specified SET.
---
doc/coreutils.texi | 30 +++++++++++++++++-------------
src/tr.c | 9 ++++-----
2 files changed, 21 insertions(+), 18 deletions(-)
diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index 88e1650..d2175cf 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -297,7 +297,7 @@ Operating on characters
* Character sets:: Specifying sets of characters
* Translating:: Changing one set of characters to another
-* Squeezing:: Squeezing repeats and deleting
+* Squeezing and deleting:: Removing characters
Directory listing
@@ -1609,7 +1609,8 @@ if @option{-b} is in effect.
@opindex -s
@opindex --squeeze-blank
@cindex squeezing empty lines
-Suppress repeated adjacent empty lines; output just one empty line
+@cindex squeezing blank lines
+Suppress repeated adjacent blank lines; output just one empty line
instead of several.
@item -t
@@ -4968,9 +4969,9 @@ may be better suited for output direct to users.
@macro ambiguousGroupNote
Note that when groups are delimited and the input stream contains
-two or more consecutive blank lines, then the output is ambiguous.
-To avoid that, filter the input through @samp{tr -s '\\n'} to replace
-each sequence of consecutive newlines with a single newline.
+blank lines, then the output is ambiguous.
+To avoid that, filter the input through @samp{tr -s '\\n'} to
+remove blank lines.
@end macro
@ambiguousGroupNote
@@ -6215,7 +6216,7 @@ options. @xref{Common options}. Options must precede operands.
@menu
* Character sets:: Specifying sets of characters.
* Translating:: Changing one set of characters to another.
-* Squeezing:: Squeezing repeats and deleting.
+* Squeezing and deleting:: Removing characters.
@end menu
@@ -6438,18 +6439,20 @@ tr -cs '[:alnum:]' '[\n*]'
@end example
-@node Squeezing
+@node Squeezing and deleting
@subsection Squeezing repeats and deleting
@cindex squeezing repeat characters
@cindex deleting characters
+@cindex removing characters
When given just the @option{--delete} (@option{-d}) option, @command{tr}
removes any input characters that are in @var{set1}.
-When given just the @option{--squeeze-repeats} (@option{-s}) option,
-@command{tr} replaces each input sequence of a repeated character that
-is in @var{set1} with a single occurrence of that character.
+When given just the @option{--squeeze-repeats} (@option{-s}) option
+and not translating, @command{tr} replaces each input sequence of a
+repeated character that is in @var{set1} with a single occurrence of
+that character.
When given both @option{--delete} and @option{--squeeze-repeats}, @command{tr}
first performs any deletions using @var{set1}, then squeezes repeats
@@ -6480,7 +6483,8 @@ tr -cs '[:alnum:]' '[\n*]'
@end example
@item
-Convert each sequence of repeated newlines to a single newline:
+Convert each sequence of repeated newlines to a single newline.
+I.E. delete blank lines:
@example
tr -s '\n'
@@ -17831,8 +17835,8 @@ $ tr '[:upper:]' '[:lower:]' < whats.gnu | tr -cd '[:alnum:]_ \n' |
@end smallexample
This command turns blanks into newlines. The @option{-s} option squeezes
-multiple newline characters in the output into just one. This helps us
-avoid blank lines. (The @samp{>} is the shell's ``secondary prompt.''
+multiple newline characters in the output into just one, removing
+blank lines. (The @samp{>} is the shell's ``secondary prompt.''
This is what the shell prints when it notices you haven't finished
typing in all of a command.)
diff --git a/src/tr.c b/src/tr.c
index fe6f466..8c87627 100644
--- a/src/tr.c
+++ b/src/tr.c
@@ -294,8 +294,8 @@ writing to standard output.\n\
-c, -C, --complement use the complement of SET1\n\
-d, --delete delete characters in SET1, do not translate\n\
-s, --squeeze-repeats replace each input sequence of a repeated character\n\
- that is listed in SET1 with a single occurrence\n\
- of that character\n\
+ that is listed in the last specified SET,\n\
+ with a single occurrence of that character\n\
-t, --truncate-set1 first truncate SET1 to length of SET2\n\
"), stdout);
fputs (HELP_OPTION_DESCRIPTION, stdout);
@@ -342,9 +342,8 @@ Translation occurs if -d is not given and both SET1 and SET2 appear.\n\
SET1 by repeating its last character as necessary. Excess characters\n\
of SET2 are ignored. Only [:lower:] and [:upper:] are guaranteed to\n\
expand in ascending order; used in SET2 while translating, they may\n\
-only be used in pairs to specify case conversion. -s uses SET1 if not\n\
-translating nor deleting; else squeezing uses SET2 and occurs after\n\
-translation or deletion.\n\
+only be used in pairs to specify case conversion. -s uses the last\n\
+specified SET, and occurs after translation or deletion.\n\
"), stdout);
emit_ancillary_info (PROGRAM_NAME);
}
--
2.5.0
