Is there go up line character? (Opposite of \n)
Most terminals understand ANSI escape codes. The relevant codes for this use case:
"\033[F"
– move cursor to the beginning of the previous line"\033[A"
– move cursor up one line
Example (Python):
print("\033[FMy text overwriting the previous line.")
Is there a reverse \n?
There's no "reverse newline" in the standard character set but, even if there was, you would have to apply it to each string in turn.
And, if you can do that, you can equally modify the strings to remove the newline. In other words, create a new list using the current one, with newlines removed. That would be something like:
>>> oldlist = ['hello\n', 'hallo\n', 'hell\n']
>>> oldlist
['hello\n', 'hallo\n', 'hell\n']
>>> newlist = [s.replace('\n','') for s in oldlist]
>>> newlist
['hello', 'hallo', 'hell']
That will remove all newlines from each of the strings. If you want to ensure you only replace a single newline at the end of the strings, you can instead use:
newlist = [re.sub('\n$','',s) for s in oldlist]
Go lang differentiate \n and line break
There is no distinction between a "real" and an "unreal" line break.
If you're using a Unix-like system, the end of a line in a text file is denoted by the LF or '\n'
character. You cannot have a '\n'
character in the middle of a line.
A string in memory can contain as many '\n'
characters as you like. The string "foo\nbar\n"
, when written to a text file, will create two lines, "foo"
and "bar"
.
There is no effective difference between
fmt.Println("foo")
fmt.Println("bar")
and
fmt.Printf("foo\nbar\n")
Both print the same sequence of 2 lines, as does this:
fmt.Println("foo\nbar")
Is there oldline character in Java?
ASCII doesn't standardize a "line starve" or reverse line feed control character. Some character based terminals/terminal emulators recognize control code sequences that move the cursor up a line; these aren't Java-specific, and depend on your OS and configuration. Here's a starting point if you're using Linux: http://www.kernel.org/doc/man-pages/online/pages/man4/console_codes.4.html
Difference between \n and \r?
In terms of ascii code, it's 3 -- since they're 10 and 13 respectively;-).
But seriously, there are many:
- in Unix and all Unix-like systems,
\n
is the code for end-of-line,\r
means nothing special - as a consequence, in C and most languages that somehow copy it (even remotely),
\n
is the standard escape sequence for end of line (translated to/from OS-specific sequences as needed) - in old Mac systems (pre-OS X),
\r
was the code for end-of-line instead - in Windows (and many old OSs), the code for end of line is 2 characters,
\r\n
, in this order - as a (surprising;-) consequence (harking back to OSs much older than Windows),
\r\n
is the standard line-termination for text formats on the Internet - for electromechanical teletype-like "terminals",
\r
commands the carriage to go back leftwards until it hits the leftmost stop (a slow operation),\n
commands the roller to roll up one line (a much faster operation) -- that's the reason you always have\r
before\n
, so that the roller can move while the carriage is still going leftwards!-) Wikipedia has a more detailed explanation. - for character-mode terminals (typically emulating even-older printing ones as above), in raw mode,
\r
and\n
act similarly (except both in terms of the cursor, as there is no carriage or roller;-)
In practice, in the modern context of writing to a text file, you should always use \n
(the underlying runtime will translate that if you're on a weird OS, e.g., Windows;-). The only reason to use \r
is if you're writing to a character terminal (or more likely a "console window" emulating it) and want the next line you write to overwrite the last one you just wrote (sometimes used for goofy "ascii animation" effects of e.g. progress bars) -- this is getting pretty obsolete in a world of GUIs, though;-).
What is the newline character in the C language: \r or \n?
It's \n
. When you're reading or writing text mode files, or to stdin/stdout etc, you must use \n
, and C will handle the translation for you. When you're dealing with binary files, by definition you are on your own.
What is the difference between a line feed and a carriage return?
A line feed means moving one line forward. The code is \n
.
A carriage return means moving the cursor to the beginning of the line. The code is \r
.
Windows editors often still use the combination of both as \r\n
in text files. Unix uses mostly only the \n
.
The separation comes from typewriter times, when you turned the wheel to move the paper to change the line and moved the carriage to restart typing on the beginning of a line. This was two steps.
Is there go up line character? (Opposite of \n)
Most terminals understand ANSI escape codes. The relevant codes for this use case:
"\033[F"
– move cursor to the beginning of the previous line"\033[A"
– move cursor up one line
Example (Python):
print("\033[FMy text overwriting the previous line.")
Java carriage to previous line
I don't think you can.
You would normally use System.out.print
for the first part instead and use a println()
or a '\n'
once you're sure your line ended.
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