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bash internal (293)

161

bash

This demonstrates a for loop iterating over files matching a pattern in a directory.


for i in /etc/rc.*; do
  echo "$i"
done

bash internal loops for loop globbing (wildcard)

162

bash

This code lists all items in the current directory using ls, stores them in a variable, and iterates over each item to print its name.


items=`ls .`
for item in $items; do
    echo "$item"
done

bash internal loops for loop variable expansion

163

bash

This demonstrates redirecting the output of a Python script to a file in Bash.


python hello.py > "output.out" # redirect output from the script to output.out

bash internal file and stream operations stream redirection and piping output redirection

164

bash

This demonstrates how to define a Bash function that returns a non-zero exit status to indicate an error.


myfunc() {
  return 1
}

bash internal code blocks function definition

165

bash

This demonstrates redirecting command output to /dev/null to suppress it.


ls > /dev/null

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

166

bash

This demonstrates assignment a value from standard input.


read -p "password:" PASSWORD

bash internal data manipulations other variable features variable assignment

167

bash

This demonstrates the use of ANSI-C quoting to include special characters like newline and tab in a string.


$'\n\t'

bash internal data manipulations string manipulation and expansions ANSI-C quoting

168

bash

This demonstrates the strict mode in Bash to make scripts more robust and error-resistant.


#!/usr/bin/env bash
set -euo pipefail

bash internal other builtin features shell configuration and customization strict mode

169

bash

This demonstrates multiple methods to overwrite a file with a string in Bash, including process substitution, direct redirection, piping to cat, and piping to tee.


cat > output.out <(echo "#helloworld")
echo "#helloworld" > output.out
echo "#helloworld" | cat > output.out
echo "#helloworld" | tee output.out >/dev/null

bash internal file and stream operations stream redirection and piping file output

170

bash

This demonstrates checking the exit status of a function and handling success or failure in a Bash script.


if myfunc; then
  echo "success"
else
  echo "failure"
fi

bash internal flow control tests (conditions)exit status condition

171

bash

This script demonstrates various globbing patterns (wildcards) in Bash for file matching, including single character, multi-character, character ranges, exclusions, and combinations. It also highlights special cases for matching dotfiles.


# Create some sample files
touch file1.txt file2.txt file3.txt filea.txt fileb.txt filec.txt filed.txt filee.txt filef.txt
# Examples
ls file?.txt # => file1.txt  file2.txt  file3.txt  filea.txt  fileb.txt  filec.txt  filed.txt  filee.txt	filef.txt
ls file*.txt # => file1.txt  file2.txt  file3.txt  filea.txt  fileb.txt  filec.txt  filed.txt  filee.txt	filef.txt
ls file[ab].txt # => filea.txt  fileb.txt
ls file[a-c].txt # => filea.txt  fileb.txt  filec.txt
ls file[^ab].txt # => file1.txt  file2.txt  file3.txt  filec.txt  filed.txt  filee.txt  filef.txt
ls {filea*,fileb*} # => filea.txt  fileb.txt
# Dotfile special case: filename expansion can match dotfiles, but only if the pattern explicitly includes the dot as a literal character.
## Will not expand to ~/.bashrc: wildcards and metacharacters will NOT expand to a dot in globbing. Setting the "dotglob" option turns this off.
ls ~/[.]bashrc    # => No such file or directory
ls ~/?bashrc      # => No such file or directory
ls ~/.[b]ashrc    # => ~/.bashrc
ls ~/.ba?hrc      # => ~/.bashrc
ls ~/.bashr*      # => ~/.bashrc
# Clean up the created files
rm file1.txt file2.txt file3.txt filea.txt fileb.txt filec.txt filed.txt filee.txt filef.txt

bash internal file and stream operations pathname expansion and matching globbing (wildcards)

172

bash

linux

This demonstrates how to make a script executable by adding the execute (+x) permission.


chmod +x foo.sh

bash internal file and stream operations file permissions chmod

173

bash

This demonstrates the usage of $* to represent all positional arguments as a single string.

$*

bash internal data manipulations positional arguments all arguments ($*)

174

bash

This demonstrates running a background process with wait to ensure it completes before proceeding.


sleep 5 &
wait
echo "Background process completed"

bash internal process management background processes wait for completion

175

bash

This demonstrates accessing the name of the currently executing script using the built-in variable $0.


echo "Script name: $0"

bash internal data manipulations positional arguments script name ($0)

176

bash

This demonstrates the use of process substitution to obtain a file descriptor for a command's output.


echo <(echo "#helloworld")

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

177

bash

This demonstrates defining and calling a function in Bash, handling arguments, and retrieving return values.


function foo ()
{
    echo "Arguments work just like script arguments: $@"
    echo "And: $1 $2..."
    echo "This is a function"
    returnValue=0    # Variable values can be returned
    return $returnValue
}
# Call the function `foo` with two arguments, arg1 and arg2:
foo arg1 arg2
# => Arguments work just like script arguments: arg1 arg2
# => And: arg1 arg2...
# => This is a function
# Return values can be obtained with $?
resultValue=$?
# More than 9 arguments are also possible by using braces, e.g. ${10}, ${11}, ...

bash internal code blocks function definition

178

bash

This demonstrates checking if a file is a symbolic link using the -h conditional expression in Bash.


[[ -h FILE ]]

bash internal flow control tests (conditions)file condition

179

bash

This Bash pattern demonstrates matching specific filenames using character classes in globbing.


sales202[0123].csv

bash internal data manipulations string manipulation and expansions globbing character classes

180

bash

This demonstrates checking if a given path is a directory using the -d test operator in Bash.


[[ -d FILE ]]

bash internal flow control tests (conditions)file and directory conditions directory test (-d)

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161

bash

This demonstrates a for loop iterating over files matching a pattern in a directory.


for i in /etc/rc.*; do
  echo "$i"
done

bash internal loops for loop globbing (wildcard)

162

bash

This code lists all items in the current directory using ls, stores them in a variable, and iterates over each item to print its name.


items=`ls .`
for item in $items; do
    echo "$item"
done

bash internal loops for loop variable expansion

163

bash

This demonstrates redirecting the output of a Python script to a file in Bash.


python hello.py > "output.out" # redirect output from the script to output.out

bash internal file and stream operations stream redirection and piping output redirection

164

bash

This demonstrates how to define a Bash function that returns a non-zero exit status to indicate an error.


myfunc() {
  return 1
}

bash internal code blocks function definition

165

bash

This demonstrates redirecting command output to /dev/null to suppress it.


ls > /dev/null

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

166

bash

This demonstrates assignment a value from standard input.


read -p "password:" PASSWORD

bash internal data manipulations other variable features variable assignment

167

bash

This demonstrates the use of ANSI-C quoting to include special characters like newline and tab in a string.


$'\n\t'

bash internal data manipulations string manipulation and expansions ANSI-C quoting

168

bash

This demonstrates the strict mode in Bash to make scripts more robust and error-resistant.


#!/usr/bin/env bash
set -euo pipefail

bash internal other builtin features shell configuration and customization strict mode

169

bash

This demonstrates multiple methods to overwrite a file with a string in Bash, including process substitution, direct redirection, piping to cat, and piping to tee.


cat > output.out <(echo "#helloworld")
echo "#helloworld" > output.out
echo "#helloworld" | cat > output.out
echo "#helloworld" | tee output.out >/dev/null

bash internal file and stream operations stream redirection and piping file output

170

bash

This demonstrates checking the exit status of a function and handling success or failure in a Bash script.


if myfunc; then
  echo "success"
else
  echo "failure"
fi

bash internal flow control tests (conditions)exit status condition

171

bash


# Create some sample files
touch file1.txt file2.txt file3.txt filea.txt fileb.txt filec.txt filed.txt filee.txt filef.txt
# Examples
ls file?.txt # => file1.txt  file2.txt  file3.txt  filea.txt  fileb.txt  filec.txt  filed.txt  filee.txt	filef.txt
ls file*.txt # => file1.txt  file2.txt  file3.txt  filea.txt  fileb.txt  filec.txt  filed.txt  filee.txt	filef.txt
ls file[ab].txt # => filea.txt  fileb.txt
ls file[a-c].txt # => filea.txt  fileb.txt  filec.txt
ls file[^ab].txt # => file1.txt  file2.txt  file3.txt  filec.txt  filed.txt  filee.txt  filef.txt
ls {filea*,fileb*} # => filea.txt  fileb.txt
# Dotfile special case: filename expansion can match dotfiles, but only if the pattern explicitly includes the dot as a literal character.
## Will not expand to ~/.bashrc: wildcards and metacharacters will NOT expand to a dot in globbing. Setting the "dotglob" option turns this off.
ls ~/[.]bashrc    # => No such file or directory
ls ~/?bashrc      # => No such file or directory
ls ~/.[b]ashrc    # => ~/.bashrc
ls ~/.ba?hrc      # => ~/.bashrc
ls ~/.bashr*      # => ~/.bashrc
# Clean up the created files
rm file1.txt file2.txt file3.txt filea.txt fileb.txt filec.txt filed.txt filee.txt filef.txt

bash internal file and stream operations pathname expansion and matching globbing (wildcards)

172

bash

linux

This demonstrates how to make a script executable by adding the execute (+x) permission.


chmod +x foo.sh

bash internal file and stream operations file permissions chmod

173

bash

This demonstrates the usage of $* to represent all positional arguments as a single string.

$*

bash internal data manipulations positional arguments all arguments ($*)

174

bash

This demonstrates running a background process with wait to ensure it completes before proceeding.


sleep 5 &
wait
echo "Background process completed"

bash internal process management background processes wait for completion

175

bash

This demonstrates accessing the name of the currently executing script using the built-in variable $0.


echo "Script name: $0"

bash internal data manipulations positional arguments script name ($0)

176

bash

This demonstrates the use of process substitution to obtain a file descriptor for a command's output.


echo <(echo "#helloworld")

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

177

bash

This demonstrates defining and calling a function in Bash, handling arguments, and retrieving return values.


function foo ()
{
    echo "Arguments work just like script arguments: $@"
    echo "And: $1 $2..."
    echo "This is a function"
    returnValue=0    # Variable values can be returned
    return $returnValue
}
# Call the function `foo` with two arguments, arg1 and arg2:
foo arg1 arg2
# => Arguments work just like script arguments: arg1 arg2
# => And: arg1 arg2...
# => This is a function
# Return values can be obtained with $?
resultValue=$?
# More than 9 arguments are also possible by using braces, e.g. ${10}, ${11}, ...