Redirecting man page output to file results in double letters in words
The 'man' program was originally designed to print its output on teletypes, and uses over-printing to produce bold character and underlining effects. What you're actually seeing is the effect of the file containing strings of the form X^HX, where the ^H is a backspace character. You also have strings like _^HX, for underlining (hence the _f_i_l_e).
These can be stripped easily using a text editor like vi, which will display the backspaces.
:%s/_^H//g
will remove the underlines, and
:%s/.^H.//g
the boldings (the ^H in the above is ctrl-H. You will have to use ctrl-V ctrl-H to enter these into vi.
How to Switch between writing to file and printing in C
how can switch between two
Use a temprary file descriptor to store stdout.
In bash you could practice it:
exec {tempfd}<&1 # copy stdout to temporary fd
exec 1>./foo.txt # redirect to file
man man
exec 1>&${tempfd} # restore stdout
echo welcome back to terminal output
Similar in C:
#include <stdio.h>
#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
int main(void) {
int tempfd = dup(STDOUT_FILENO); // exec {tempfd}<&1
int filefd = open("./foo.txt", O_WRONLY | O_CREAT | O_TRUNC);
dup2(filefd, STDOUT_FILENO); // exec 1>./foo.txt
system("echo man man");
dup2(tempfd, STDOUT_FILENO); // exec 1>&${tempfd}
printf("welcome back to terminal output\n");
system("echo ---- THIS IS IN foo.txt file: ---");
system("cat foo.txt");
return 0;
}
outputs on repl:
welcome back to terminal output
---- THIS IS IN foo.txt file: ---
man man
last problem is my foo.txt is wrong there are outputs like (MMAANNUUAALL SSEECCTTIIOONNSS)
Redirecting man page output to file results in double letters in words
I am pretty new to both c
Compile with all possible warnings -Wall -Wextra. Check your programs with sanitizer -fsanitize=address and with valgrind for correctness.
What does 2 &1 mean?
File descriptor 1 is the standard output (stdout).
File descriptor 2 is the standard error (stderr).
At first, 2>1 may look like a good way to redirect stderr to stdout. However, it will actually be interpreted as "redirect stderr to a file named 1".
& indicates that what follows and precedes is a file descriptor, and not a filename. Thus, we use 2>&1. Consider >& to be a redirect merger operator.
Output redirection hangs if process has spawned a background fork of xclip
By default,
- all open files are passed from a parent process to child process. AND
- When a pipe is created (A->B), process B will not get the EOF indicator on stdin, until ALL processes from step A close their STDOUT.
Combining the above, when you execute /script.sh | ./another_script.sh, the backgrounded xclip will inherit the 'script.sh' stdout (which is the input to ./another_script.sh), at this time, there are two processes (script.sh, xclip) which are connected to the pipe. Only when both will close STDOUT (or will terminate), the ./another_script.sh will see the EOF on the pipe, and will be able to exit (assuming it's waiting for EOF on input).
The solution for those cases is for the back-grounded process to close stdout, therefore allowing pipelines to complete. Usually, the stdout will be redirected to stderr, if output is needed. Most likely, the '-f' closes the STDOUT.
Per man xclip, possible to write echo $RESULT | xclip -f (no need for extra echo) to avoid the problem, and allow script to run as part of a pipeline
man fork and man pipe provides the details. In particular
man 2 fork:
- The child inherits copies of the parent's set of open file descriptors. Each file descriptor in the child refers to the same
open file description (see open(2)) as the corresponding file descriptor in the parent. This means that the two file descrip‐
tors share open file status flags, file offset, and signal-driven I/O attributes (see the description of F_SETOWN and
F_SETSIG
in fcntl(2)).
man 7 pipe:
If all file descriptors referring to the write end of a pipe have been closed,
then an attempt to read(2) from the pipe will see
end-of-file (read(2) will return 0).
How to properly use dvioptions in preview functon from sympy?
These look like the command line options of dvipng. You can see a full list if you run man dvipng:
DVIPNG(1) User commands DVIPNG(1)
NAME
dvipng - A DVI-to-PNG translator
SYNOPSIS
dvipng [options] filename
dvipng [options] [filename] -
DESCRIPTION
This program makes PNG and/or GIF graphics from DVI files as obtained
from TeX and its relatives.
If GIF support is enabled, GIF output is chosen by using the dvigif
binary or with the --gif option.
The benefits of dvipng/dvigif include
o Speed. It is a very fast bitmap-rendering code for DVI files, which
makes it suitable for generating large amounts of images on-the-
fly, as needed in preview-latex, WeBWorK and others.
o It does not read the postamble, so it can be started before TeX
finishes. There is a --follow switch that makes dvipng wait at end-
of-file for further output, unless it finds the POST marker that
indicates the end of the DVI.
o Interactive query of options. dvipng can read options interactively
through stdin, and all options are usable. It is even possible to
change the input file through this interface.
o Supports PK, VF, PostScript Type1, and TrueType fonts, subfonts
(i.e., as used in CJK-LaTeX), color specials, and inclusion of
PostScript, PNG, JPEG or GIF images.
o and more...
OPTIONS
Many of the parameterless options listed here can be turned off by
suffixing the option with a zero (0); for instance, to turn off page
reversal, use -r0. Such options are marked with a trailing *.
- Read additional options from standard input after processing the
command line.
--help
Print a usage message and exit.
--version
Print the version number and exit.
-bd num
-bd color_spec
-bd 'num color_spec'
Set the pixel width of the transparent border (default 0). Using
this option will make the image edges transparent, but it only
affects pixels with the background color. Giving a color_spec will
set the fallback color, to be used in viewers that cannot handle
transparency (the default is the background color). The color spec
should be in TeX color \special syntax, e.g., 'rgb 1.0 0.0 0.0'.
Setting the fallback color makes the default border width 1 px.
--bdpi num
This option only has an effect when using bitmapped (PK) fonts. The
option sets the base (Metafont) resolution, both horizontal and
vertical, to num dpi (dots per inch). This option is necessary when
manually selecting Metafont mode with the --mode option (see
below).
-bg color_spec
Choose background color for the images. This option will be ignored
if there is a background color \special in the DVI. The color spec
should be in TeX color \special syntax, e.g., 'rgb 1.0 0.0 0.0'.
You can also specify 'Transparent' or 'transparent' which will give
you a transparent background with the normal background as a
fallback color. A capitalized 'Transparent' will give a full-alpha
transparency, while an all-lowercase 'transparent' will give a
simple fully transparent background with non-transparent
antialiased pixels. The latter would be suitable for viewers who
cannot cope with a true alpha channel. GIF images do not support
full alpha transparency, so in case of GIF output, both variants
will use the latter behaviour.
-d num
Set the debug flags, showing what dvipng (thinks it) is doing. This
will work unless dvipng has been compiled without the "DEBUG"
option (not recommended). Set the flags as you need them, use -d -1
as the first option for maximum output.
-D num
Set the output resolution, both horizontal and vertical, to num dpi
(dots per inch).
One may want to adjust this to fit a certain text font size (e.g.,
on a web page), and for a text font height of font_px pixels (in
Mozilla) the correct formula is
<dpi> = <font_px> * 72.27 / 10 [px * TeXpt/in / TeXpt]
The last division by ten is due to the standard font height 10pt in
your document, if you use 12pt, divide by 12. Unfortunately, some
proprietary browsers have font height in pt (points), not pixels.
You have to rescale that to pixels, using the screen resolution
(default is usually 96 dpi) which means the formula is
<font_px> = <font_pt> * 96 / 72 [pt * px/in / (pt/in)]
On some high-res screens, the value is instead 120 dpi. Good luck!
--depth*
Report the depth of the image. This only works reliably when the
LaTeX style preview.sty from preview-latex is used with the active
option. It reports the number of pixels from the bottom of the
image to the baseline of the image. This can be used for vertical
positioning of the image in, e.g., web documents, where one would
use (Cascading StyleSheets 1)
<IMG SRC="<filename.png>" STYLE="vertical-align: -<depth>px">
The depth is a negative offset in this case, so the minus sign is
necessary, and the unit is pixels (px).
--dvinum*
Set this option to make the output page number be the TeX page
numbers rather than the physical page number. See the -o switch.
-fg color_spec
Choose foreground color for the images. This option will be ignored
if there is a foreground color \special in the DVI. The color spec
should be in TeX color \special syntax, e.g., 'rgb 1.0 0.0 0.0'.
--follow*
Wait for data at end-of-file. One of the benefits of dvipng is that
it does not read the postamble, so it can be started before TeX
finishes. This switch makes dvipng wait at end-of-file for further
output, unless it finds the POST marker that indicates the end of
the DVI. This is similar to tail -f but for DVI-to-PNG conversion.
--freetype*
Enable/disable FreeType font rendering (default on). This option is
available if the FreeType2 font library was present at compilation
time. If this is the case, dvipng will have direct support for
PostScript Type1 and TrueType fonts internally, rather than using
gsftopk for rendering the fonts. If you have PostScript versions of
Computer Modern installed, there will be no need to generate
bitmapped (PK) variants on disk of these. Then, you can render
images at different (and unusual) resolutions without cluttering
the disk with lots of bitmapped fonts. One reason to disable
FreeType font rendering would be to generate identical output on
different platforms, since FreeType uses the native renderer and
therefore can give slightly different output on each platform.
--gamma num
Control the interpolation of colors in the greyscale anti-aliasing
color palette. Default value is 1.0. For 0 < num < 1, the fonts
will be lighter (more like the background), and for num > 1, the
fonts will be darker (more like the foreground).
--gif*
The images are output in the GIF format, if GIF support is enabled.
This is the default for the dvigif binary, which only will be
available when GIF support is enabled. GIF images are palette
images (see the --palette option) and does not support true alpha
channels (see the --bg option). See also the --png option.
--height*
Report the height of the image. This only works reliably when the
LaTeX style preview.sty from preview-latex is used with the active
option. It reports the number of pixels from the top of the image
to the baseline of the image. The total height of the image is
obtained as the sum of the values reported from --height and
--depth.
-l [=]num
The last page printed will be the first one numbered num. Default
is the last page in the document. If num is prefixed by an equals
sign, then it (and the argument to the -p option, if specified) is
treated as a physical (absolute) page number, rather than a value
to compare with the TeX \count0 values stored in the DVI file.
Thus, using -l =9 will end with the ninth page of the document, no
matter what the pages are actually numbered.
--mode mode
This option only has an effect when using bitmapped (PK) fonts. Use
mode as the Metafont device name for the PK fonts (both for path
searching and font generation). This needs to be augmented with the
base device resolution, given with the --bdpi option. See the file
<ftp://ftp.tug.org/tex/modes.mf> for a list of resolutions and mode
names for most devices.
-M* This option only has an effect when using bitmapped (PK) fonts. It
turns off automatic PK font generation (mktexpk).
--nogs*
This switch prohibits the internal call to GhostScript for
displaying PostScript specials. --nogs0 turns the call back on.
--nogssafer*
Normally, if GhostScript is used to render PostScript specials, the
GhostScript interpreter is run with the option -dSAFER. The
--nogssafer option runs GhostScript without -dSAFER. The -dSAFER
option in Ghostscript disables PostScript operators such as
deletefile, to prevent possibly malicious PostScript programs from
having any effect.
--norawps*
Some packages generate raw PostScript specials, even non-rendering
such specials. This switch turns off the internal call to
GhostScript intended to display these raw PostScript specials.
--norawps0 turns the call back on.
-o name
Send output to the file name. A single occurrence of %d or %01d,
..., %09d will be exchanged for the physical page number (this can
be changed, see the --dvinum switch). The default output filename
is file%d.png where the input DVI file was file.dvi.
-O x-offset,y-offset
Move the origin by x-offset,y-offset, a comma-separated pair of
dimensions such as .1in,-.3cm. The origin of the page is shifted
from the default position (of one inch down, one inch to the right
from the upper left corner of the paper) by this amount.
-p [=]num
The first page printed will be the first one numbered num. Default
is the first page in the document. If num is prefixed by an equals
sign, then it (and the argument to the -l option, if specified) is
treated as a physical (absolute) page number, rather than a value
to compare with the TeX \count0 values stored in the DVI file.
Thus, using -p =3 will start with the third page of the document,
no matter what the pages are actually numbered.
--palette*
When an external image is included, dvipng will automatically
switch to truecolor mode, to avoid unnecessary delay and quality
reduction, and enable the EPS translator to draw on a transparent
background and outside of the boundingbox. This switch will force
palette (256-color) output and make dvipng revert to opaque clipped
image inclusion. This will also override the --truecolor switch if
present.
--picky*
No images are output when a warning occurs. Normally, dvipng will
output an image in spite of a warning, but there may be something
missing in this image. One reason to use this option would be if
you have a more complete but slower fallback converter. Mainly,
this is useful for failed figure inclusion and unknown \special
occurrences, but warnings will also occur for missing or unknown
color specs and missing PK fonts.
--png*
The images are output in the PNG format. This is the default for
the dvipng binary. See also the --gif option.
-pp firstpage-lastpage
Print pages firstpage through lastpage; but not quite equivalent to
-p firstpage -l lastpage. For example, when rendering a book, there
may be several instances of a page in the DVI file (one in
"\frontmatter", one in "\mainmatter", and one in "\backmatter"). In
case of several pages matching, -pp firstpage-lastpage will render
all pages that matches the specified range, while -p firstpage -l
lastpage will render the pages from the first occurrence of
firstpage to the first occurrence of lastpage. This is the
(undocumented) behaviour of dvips. In dvipng you can give both
kinds of options, in which case you get all pages that matches the
range in -pp between the pages from -p to -l. Also multiple -pp
options accumulate, unlike -p and -l. The - separator can also be
:. Note that -pp -1 will be interpreted as "all pages up to and
including 1", if you want a page numbered -1 (only the table of
contents, say) put -pp -1--1, or more readable, -pp -1:-1.
-q* Run quietly. Don't chatter about pages converted, etc. to standard
output; report no warnings (only errors) to standard error.
-Q num
Set the quality to num. That is, choose the number of antialiasing
levels for bitmapped fonts (PK), to be num*num+1. The default value
is 4 which gives 17 levels of antialiasing for antialiased fonts
from these two. If FreeType is available, its rendering is
unaffected by this option.
-r* Toggle output of pages in reverse/forward order. By default, the
first page in the DVI is output first.
--strict*
The program exits when a warning occurs. Normally, dvipng will
output an image in spite of a warning, but there may be something
missing in this image. One reason to use this option would be if
you have a more complete but slower fallback converter. See the
--picky option above for a list of when warnings occur.
-T image_size
Set the image size to image_size which can be either of bbox,
tight, or a comma-separated pair of dimensions hsize,vsize such as
.1in,.3cm. The default is bbox which produces a PNG that includes
all ink put on the page and in addition the DVI origin, located 1in
from the top and 1in from the left edge of the paper. This usually
gives whitespace above and to the left in the produced image. The
value tight will make dvipng only include all ink put on the page,
producing neat images.
--truecolor*
This will make dvipng generate truecolor output. Note that
truecolor output is automatic if you include an external image in
your DVI, e.g., via a PostScript special (i.e., the graphics or
graphicx package). This switch is overridden by the --palette
switch.
-v* Enable verbose operation. This will currently indicate what fonts
is used, in addition to the usual output.
--width*
Report the width of the image. See also --height and --depth.
-x num
This option is deprecated; it should not be used. It is much better
to select the output resolution directly with the -D option. This
option sets the magnification ratio to num/1000 and overrides the
magnification specified in the DVI file. Must be between 10 and
100000. It is recommended that you use standard magstep values
(1095, 1200, 1440, 1728, 2074, 2488, 2986, and so on) to help
reduce the total number of PK files generated. num may be a real
number, not an integer, for increased precision.
-z num
Set the PNG compression level to num. This option is enabled if
your libgd is new enough. The default compression level is 1, which
selects maximum speed at the price of slightly larger PNGs. For an
older libgd, the hard-soldered value 5 is used. The include file
png.h says "Currently, valid values range from 0 - 9, corresponding
directly to the zlib compression levels 0 - 9 (0 - no compression,
9 - "maximal" compression). Note that tests have shown that zlib
compression levels 3-6 usually perform as well as level 9 for PNG
images, and do considerably fewer calculations. In the future,
these values may not correspond directly to the zlib compression
levels."
NOTES
The full manual is accessible in info format, on most systems by typing
info dvipng
COPYRIGHT
This program is released under the GNU Lesser General Public License
version 3, see the COPYING file in the dvipng distribution or
<http://www.gnu.org/licenses/gpl.html>.
Copyright (c) 2002-2015, 2019 Jan-AAke Larsson
dvipng (TeX Live) 1.17 2021-02-26 DVIPNG(1)
How to capture cURL output to a file?
curl -K myconfig.txt -o output.txt
Writes the first output received in the file you specify (overwrites if an old one exists).
curl -K myconfig.txt >> output.txt
Appends all output you receive to the specified file.
Note: The -K is optional.
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