Shell/Bash¶

Error handling¶

set -o errexit
set -o errtrace
set -o pipefail
set -o nounset

Count chars in string¶

$ foo="Test123"
$ grep -o "s" <<<"$foo" | wc -l
7

IFs¶

Check if the given string exists in given stuff¶

$ foo="Test123"
$ if foo | grep -q "Test"; then echo "Test exists in foo"; fi

Remove leading and trailing spaces¶

FOO=' test test test '
FOO_NO_EXTERNAL_SPACE="$(echo -e "${FOO}" | sed -e 's/^[[:space:]]*//' -e 's/[[:space:]]*$//')"
echo -e "FOO_NO_EXTERNAL_SPACE='${FOO_NO_EXTERNAL_SPACE}'"
# > FOO_NO_EXTERNAL_SPACE='test test test'
echo -e "length(FOO_NO_EXTERNAL_SPACE)==${#FOO_NO_EXTERNAL_SPACE}"
# > length(FOO_NO_EXTERNAL_SPACE)==14

Source: https://stackoverflow.com/questions/369758/how-to-trim-whitespace-from-a-bash-variable

Styling¶

Bold, Italic, Underline, etc.¶

echo -e '\033[1mYOUR_STRING\033[0m'

Explanation:

echo -e - The -e option means that escaped (backslashed) strings will be interpreted
\033 - escaped sequence represents beginning/ending of the style
lowercase m - indicates the end of the sequence
1 - Bold attribute (see below for more)
[0m - resets all attributes, colors, formatting, etc.

The possible integers are:

0 - Normal Style
1 - Bold
2 - Dim
3 - Italic
4 - Underlined
5 - Blinking
7 - Reverse
8 - Invisible

Source: https://stackoverflow.com/a/42449998

History¶

Show history for specific date(s)¶

# Samples:
# history-by-date 2025-02-15
# history-by-date "2025-02-15|2025-02-16"
function history-by-date() {
    history 0 | awk '{for(i=2;i<=NF;i++){ printf("%s",( (i>2) ? OFS : "" ) $i) } ; print "";}' | grep --color=never -E "^($1)"
}