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Feature Group

bash internal (293)

Feature Group

bash internal (293)

121

bash

This demonstrates using process substitution with diff to compare the contents of two directories directly.


diff <(ls dir1) <(ls dir2)

bash internal file and stream operations stream redirection and piping process substitution

122

bash

This demonstrates the use of the $_ special variable in Bash to access and reuse the last argument from the previous command.

$_

bash internal bash special variables $_

123

bash

This demonstrates how to check if a string is empty using the -z conditional expression in Bash.


[[ -z STRING ]]

bash internal flow control tests (conditions)string condition

124

bash

This demonstrates how to get the length of a string stored in a variable using ${#variable}.


echo "${#variable}"

bash internal data manipulations string manipulation and expansions parameter expansion string length

125

bash

This demonstrates providing a default value for a variable if it is unset or empty using parameter expansion in Bash.


echo "${foo:-"DefaultValueIfFooIsMissingOrEmpty"}"
# => DefaultValueIfFooIsMissingOrEmpty
# This works for null (foo=) and empty string (foo=""); zero (foo=0) returns 0.
# Note that it only returns default value and doesn't change variable value.

bash internal data manipulations string manipulation and expansions parameter expansion default value substitution

126

bash

This demonstrates checking if a string is non-empty using the -n condition in Bash.


[[ -n STRING ]]

bash internal flow control tests (conditions)string condition

127

bash

This demonstrates basic string comparison using double square brackets [[ ]] in Bash.


[[ STRING == STRING ]]

bash internal flow control tests (conditions)string condition

128

bash

This demonstrates two ways to print the current directory in Bash: using command substitution and a built-in variable.


echo "I'm in $(pwd)" # execs `pwd` and interpolates output
echo "I'm in $PWD" # interpolates the variable

bash internal data manipulations string manipulation and expansions command substitution

129

bash

This demonstrates the use of the clear command to clear the terminal screen, with an alternative method (Ctrl-L) noted in the comment.


clear
# Ctrl-L also works for clearing output.

bash internal process management commands terminal management clear screen

130

bash

This demonstrates iterating over a range of numbers with a specified step size using a for loop in Bash.


for i in {5..50..5}; do
    echo "Welcome $i"
done

bash internal loops for loop range with step

131

bash

This demonstrates the use of Bash's built-in $RANDOM variable to generate and print a random number.


echo "Random number: $RANDOM"

bash internal other builtin features built-in variables random number generation

132

bash

This demonstrates checking if a file or directory exists using the -e flag in a conditional expression.


[[ -e FILE ]]

bash internal flow control tests (conditions)file and directory conditions

133

bash

This demonstrates a forever (infinite) while loop that executes a command and sleeps for 10 seconds repeatedly.


while true; do 
  # example_command_to_execute
  echo "--- sleep 10 ---"
  sleep 10
done

bash internal loops while loop forever (infinite)

134

bash

This demonstrates checking if a file exists and is readable using the -r conditional expression.


[[ -r FILE ]]

bash internal flow control tests (conditions)file condition

135

bash

This demonstrates capturing a single keystroke from the user without requiring them to press Enter.


read -n 1 answer    # Just one character

bash internal data manipulations other variable features variable assignment

136

bash

This demonstrates extracting the directory path of the current script by removing the filename from the script's path.


dir=${0%/*}

bash internal data manipulations string manipulation and expansions parameter expansion path manipulation

137

bash

This demonstrates the use of brace expansion in Bash to generate multiple strings from a single pattern.


echo {A,B}.js

bash internal data manipulations string manipulation and expansions parameter expansion brace expansion

138

bash

This demonstrates the usage of the $! special variable to store the process ID (PID) of the last background command.

$!

bash internal data manipulations process management background process pid

139

bash

This demonstrates reading and processing a file line-by-line using a while loop in Bash.


while read -r line; do
  echo "$line"
done <file.txt

bash internal loops while loop line-by-line

140

bash

This demonstrates printing the current working directory using the $PWD built-in variable.


echo "Current directory: $PWD"

bash internal data manipulations other variable features built-in variables

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121

bash

This demonstrates using process substitution with diff to compare the contents of two directories directly.


diff <(ls dir1) <(ls dir2)

bash internal file and stream operations stream redirection and piping process substitution

122

bash

This demonstrates the use of the $_ special variable in Bash to access and reuse the last argument from the previous command.

$_

bash internal bash special variables $_

123

bash

This demonstrates how to check if a string is empty using the -z conditional expression in Bash.


[[ -z STRING ]]

bash internal flow control tests (conditions)string condition

124

bash

This demonstrates how to get the length of a string stored in a variable using ${#variable}.


echo "${#variable}"

bash internal data manipulations string manipulation and expansions parameter expansion string length

125

bash

This demonstrates providing a default value for a variable if it is unset or empty using parameter expansion in Bash.


echo "${foo:-"DefaultValueIfFooIsMissingOrEmpty"}"
# => DefaultValueIfFooIsMissingOrEmpty
# This works for null (foo=) and empty string (foo=""); zero (foo=0) returns 0.
# Note that it only returns default value and doesn't change variable value.

bash internal data manipulations string manipulation and expansions parameter expansion default value substitution

126

bash

This demonstrates checking if a string is non-empty using the -n condition in Bash.


[[ -n STRING ]]

bash internal flow control tests (conditions)string condition

127

bash

This demonstrates basic string comparison using double square brackets [[ ]] in Bash.


[[ STRING == STRING ]]

bash internal flow control tests (conditions)string condition

128

bash

This demonstrates two ways to print the current directory in Bash: using command substitution and a built-in variable.


echo "I'm in $(pwd)" # execs `pwd` and interpolates output
echo "I'm in $PWD" # interpolates the variable

bash internal data manipulations string manipulation and expansions command substitution

129

bash

This demonstrates the use of the clear command to clear the terminal screen, with an alternative method (Ctrl-L) noted in the comment.


clear
# Ctrl-L also works for clearing output.

bash internal process management commands terminal management clear screen

130

bash

This demonstrates iterating over a range of numbers with a specified step size using a for loop in Bash.


for i in {5..50..5}; do
    echo "Welcome $i"
done

bash internal loops for loop range with step

131

bash

This demonstrates the use of Bash's built-in $RANDOM variable to generate and print a random number.


echo "Random number: $RANDOM"

bash internal other builtin features built-in variables random number generation

132

bash

This demonstrates checking if a file or directory exists using the -e flag in a conditional expression.


[[ -e FILE ]]

bash internal flow control tests (conditions)file and directory conditions

133

bash

This demonstrates a forever (infinite) while loop that executes a command and sleeps for 10 seconds repeatedly.


while true; do 
  # example_command_to_execute
  echo "--- sleep 10 ---"
  sleep 10
done

bash internal loops while loop forever (infinite)

134

bash

This demonstrates checking if a file exists and is readable using the -r conditional expression.


[[ -r FILE ]]

bash internal flow control tests (conditions)file condition

135

bash

This demonstrates capturing a single keystroke from the user without requiring them to press Enter.


read -n 1 answer    # Just one character

bash internal data manipulations other variable features variable assignment

136

bash

This demonstrates extracting the directory path of the current script by removing the filename from the script's path.


dir=${0%/*}

bash internal data manipulations string manipulation and expansions parameter expansion path manipulation

137

bash

This demonstrates the use of brace expansion in Bash to generate multiple strings from a single pattern.


echo {A,B}.js

bash internal data manipulations string manipulation and expansions parameter expansion brace expansion

138

bash

This demonstrates the usage of the $! special variable to store the process ID (PID) of the last background command.

$!

bash internal data manipulations process management background process pid

139

bash

This demonstrates reading and processing a file line-by-line using a while loop in Bash.


while read -r line; do
  echo "$line"
done <file.txt

bash internal loops while loop line-by-line

140

bash

This demonstrates printing the current working directory using the $PWD built-in variable.


echo "Current directory: $PWD"

bash internal data manipulations other variable features built-in variables

Previous 1

...

6 7 8

...

15 Next