106
votes
Accepted
Is Vim immune to copy-paste attack?
Short answer: In many situations, Vim is vulnerable to this kind of attack (when pasting text in Insert mode).
Proof of concept
Using the linked article as a starting point, I was able to quickly ...
45
votes
Accepted
How do some tools (e.g. nano , less) manage to leave no content in terminals after exit?
There are two worldviews here:
As far as programs using termcap/terminfo are concerned, your terminal potentially has two modes: cursor addressing mode and scrolling mode. The latter is the normal ...
- 62.3k
40
votes
Accepted
How to use less in a script without getting ESC escape characters?
Use -R flag:
-r or --raw-control-chars
Causes "raw" control characters to be displayed. The default is to
display control characters using the caret notation; for example, a
control-A (...
- 11.9k
40
votes
Accepted
Using `printf` to print variable containing `%` percent sign results in "bash: printf: `p': invalid format character"
Use printf in its normal form:
printf '%s\n' "${TEST}"
From man printf:
SYNOPSIS
printf FORMAT [ARGUMENT]...
You should never pass a variable to the FORMAT string as it may lead to errors and ...
- 20.7k
40
votes
Accepted
How do you output a multi-line string that includes slashes and other special characters?
In this case, I'd use cat with a (quoted) here-document:
cat <<'END_CAT'
/\_/\
( o.o )
> ^ <
END_CAT
This is the best way of ensuring the ASCII art is outputted the way it is intended ...
- 12.9k
35
votes
How to escape quotes in shell?
Simple example of escaping quotes in shell:
$ echo 'abc'\''abc'
abc'abc
$ echo "abc"\""abc"
abc"abc
It's done by finishing already opened one ('), placing escaped one (\'), then opening another one (...
- 18.3k
31
votes
Accepted
Is it possible to use ANSI color escape codes in Bash here-documents?
In your script, these assignments
normal='\e[0m'
yellow='\e[33m'
put those characters literally into the variables, i.e., \e[0m, rather than the escape sequence. You can construct an escape ...
- 71.1k
29
votes
Accepted
How do I use grep while keeping the original text color?
You could do this,
x | grep --color=never hello
To quickly test it, you can do,
ls -l /etc/ --color=always | grep --color=never .
- 50.9k
28
votes
Accepted
Weird symbols on screen when using grep?
The screenshot appears to show mangled ANSI colour codes, which control text rendering. Bold/bright text is produced with the sequence ␛[1m, which is usually interpreted by your terminal and ...
- 70.6k
28
votes
Accepted
awk print apostrophe/single quote
Here are a couple of ways:
use octal escape sequences. On ASCII-based systems where ' is encoded as byte 39 (octal 047), that would be:
awk '{print "\047" $0 "\047"}' input
'...
- 72.4k
27
votes
Accepted
Why do I have to escape a "dot" twice?
Generally, you only have to escape one time to make special character considered literal. Sometime you have to do it twice, because your pattern is used by more than one program.
Let's discuss your ...
- 144k
25
votes
Accepted
Caret square bracket square bracket A ^[[A - What does it mean?
These are ANSI escape codes. The ^[ represents an ESC (escape) character, the next [ is an actual left square bracket, and the letter indicates the function of the escape code. The Esc[ part is called ...
- 6,883
23
votes
Accepted
What does the ^ character mean in sequences like ^X^I?
^c is a common notation for Ctrl+c where c is a (uppercase) letter or one of @[\]^_. It designates the corresponding control character. The correspondence is that the numeric code of the control ...
22
votes
Accepted
How to prevent random console output from breaking the terminal?
No:
there is no standard way to "disable it", and
the details of breakage are actually terminal-specific, but
there are some commonly-implemented features for which you can get misbehavior.
For ...
- 71.1k
20
votes
Accepted
How to escape single quotes correctly creating an alias
To make this an alias, which is possible, you need to use double quotes around the entire value for the alias. You'll also need to escape a few things within the alias as a result, and you need to ...
slm♦
- 346k
19
votes
Accepted
Make Less highlight search patterns instead of italicizing them
Found an answer over on the superuser: https://superuser.com/questions/566082/less-doesnt-highlight-search
Looks like it has to do with your TERM setting. For example, less highlighting acts normally ...
- 306
19
votes
Accepted
Which shells support ANSI-C quoting? e.g. $'string'
$'…' is a ksh93 feature that is also present in zsh, bash, mksh, FreeBSD sh and in some builds of BusyBox sh (BusyBox ash built with ENABLE_ASH_BASH_COMPAT). It isn't present in the POSIX sh language ...
19
votes
Accepted
Escape a mm/dd/YY backup date in a file name
You can't have / (byte 0x2F on ASCII-based systems) in a file name, period.
You can use characters that look like / like ∕ (U+2215 division slash) or ⁄ (U+2044 fraction slash though found in fewer of ...
- 470k
18
votes
Using/reading/writing the null and escape characters
Printing the null character
On many recent shells you can write null character with dollar single quotes format $'\0', hexadecimal format \x00, unicode format \u0000 or \U00000000, or just as you ...
- 43.4k
17
votes
Removing control chars (including console codes / colours) from script output
There's an ansi2txt command in the colorized-logs package on Ubuntu. It removes ANSI color codes nicely, but it doesn't deal with things like progress bars produced by emitting ^H or ^M characters to ...
- 316
17
votes
Accepted
Meaning of \[\e]0; in PS1 in .bashrc
The \e]0; is an escape sequence; \e is replaced with ASCII 27 (ESC), so the terminal receives the 4 characters ESC ] 0 ; tells xterm to set icon and title bar, that ends in BEL (\a).
So the sequence ...
- 39k
16
votes
awk print apostrophe/single quote
In awk code, just put the apostrophe inside double quotes. You can concatenate strings by putting them next to each other (juxtaposition), no matter how these strings are constructed (literal, ...
15
votes
How do you output a multi-line string that includes slashes and other special characters?
Quote it with single '' or double quotes "" to prevent the <>() from being taken as operators. Then if you want it on one line, use echo -e or $' ' in Bash, mark the newlines as \n and ...
- 116k
14
votes
Make Less highlight search patterns instead of italicizing them
The mention of LESS_TERMCAP_so was incomplete. That is less's special environment variable used to override the termcap so (standout) capability. To use this capability, you have to provide a se (...
- 71.1k
14
votes
Accepted
Hide and unhide cursor with tput
In the ncurses terminal database, cvvis is used as documented in the terminfo manual page:
cursor_visible cvvis vs make cursor very
visible
...
- 71.1k
14
votes
Accepted
What is the gnome-terminal ANSI escape sequence for "CTRL + arrow/s"?
Gnome-terminal (more properly VTE) imitates some version of xterm's escape sequences. How closely it does this, depends on the version of VTE.
The relevant xterm documentation is in the PC-Style ...
- 71.1k
13
votes
How to determine the current color of the console output?
In an xterm you can get the current color RGB color codes reported by altering a color change escape to a query. Use the ESC ] Ps m - but add a ? question mark. From the docs:
If a "?" is given ...
- 55.7k
13
votes
Using `printf` to print variable containing `%` percent sign results in "bash: printf: `p': invalid format character"
You should never put variable content in the format string given to printf. Use this instead:
printf '%s\n' "${TEST}"
- 358k
Only top scored, non community-wiki answers of a minimum length are eligible