csh - Shell C
O Shell C (csh) é um shell Unix desenvolvido por Bill Joy na Universidade da Califórnia, Berkeley, lançado pela primeira vez em 1978. Projetado para fornecer uma sintaxe mais semelhante à linguagem C para uso interativo, o csh introduziu muitos recursos que se tornaram padrão em shells posteriores, incluindo histórico de comandos, aliases e controle de jobs. Embora o csh e sua versão aprimorada tcsh sejam usados principalmente para sessões interativas em vez de scripts, eles continuam importantes em certos ambientes Unix e oferecem recursos únicos que alguns usuários preferem. Compreender o csh é valioso para administradores de sistemas e usuários que o encontram em sistemas legados ou distribuições Unix específicas.
Instalação e Configuração
Variantes do Shell C
Instalando o Shell C
Definindo csh/tcsh como Shell Padrão
Arquivos de Configuração Básicos
Sintaxe e Variáveis do Shell C
Atribuição e Uso de Variáveis
Operações com Strings
Substituição de Comandos
Estruturas de Controle
Declarações Condicionais
Declarações Switch
Loops
Operações Aritméticas
Aritmética com Comando @
Ferramentas Aritméticas Externas
Aliases e Histórico
Gerenciamento de Aliases
Gerenciamento de Histórico
Controle de Jobs e Gerenciamento de Processos
Controle de Jobs
Informações de Processos
Entrada/Saída e Redirecionamento
Redirecionamento Básico de E/S
Recursos Avançados de E/S
Comandos Internos e Recursos
Comandos Internos Essenciais
Note: Since some sections were empty in the original text, I’ve left them as placeholders in the translation. If you have specific content for those sections, I can translate those as well.```bash
Check which csh variant is available
which csh /bin/csh
which tcsh /usr/bin/tcsh
Check shell version
echo $version
tcsh 6.22.04 (Astron) 2021-04-26 (x86_64-unknown-linux) options wide,nls,dl,al,kan,rh,color,filec
Check if running csh or tcsh
echo $shell /bin/tcsh
### Installing C Shell
```bash
# Ubuntu/Debian
sudo apt update && sudo apt install csh tcsh
# CentOS/RHEL/Fedora
sudo dnf install tcsh
# macOS (tcsh is usually pre-installed)
# For csh specifically:
brew install tcsh
# Arch Linux
sudo pacman -S tcsh
# FreeBSD (usually pre-installed)
pkg install tcsh
# Check installation
csh --version
tcsh --versionSetting csh/tcsh as Default Shell
# Check current shell
echo $SHELL
# Add csh to available shells
echo /bin/csh|sudo tee -a /etc/shells
echo /bin/tcsh|sudo tee -a /etc/shells
# Set tcsh as default shell (recommended over csh)
chsh -s /bin/tcsh
# Verify change (restart terminal)
echo $SHELL
/bin/tcshBasic Configuration Files
# Configuration files for csh/tcsh
~/.cshrc # Main configuration file
~/.tcshrc # tcsh-specific configuration
~/.login # Login shell configuration
~/.logout # Logout script
# Create basic .tcshrc
cat > ~/.tcshrc ``<< 'EOF'
# tcsh configuration
# Set environment variables
setenv EDITOR vi
setenv PAGER less
setenv LANG en_US.UTF-8
# Set path
set path = (/usr/local/bin /usr/bin /bin $path)
# Aliases
alias ll 'ls -l'
alias la 'ls -la'
alias h 'history'
alias .. 'cd ..'
# Prompt
set prompt = '%n@%m:%c$ '
# History
set history = 1000
set savehist = 1000
# Completion
set autolist
set complete = enhance
# Other options
set noclobber
set notify
EOF
# Source configuration
source ~/.tcshrcC Shell Syntax and Variables
Variable Assignment and Usage
# Simple variable assignment
set name = "John Doe"
set age = 30
set path_var = "/home/user"
# Using variables
echo $name
echo "Hello, $name"
echo 'Literal: $name' # Single quotes prevent expansion
# Array variables
set fruits = (apple banana orange)
set numbers = (1 2 3 4 5)
# Accessing array elements
echo $fruits[1] # First element (1-indexed)
echo $fruits[2] # Second element
echo $fruits[$#fruits] # Last element
echo $fruits[*] # All elements
echo $#fruits # Number of elements
# Environment variables
setenv PATH "/usr/local/bin:$PATH"
setenv EDITOR vi
setenv HOME /home/user
# Unset variables
unset name
unsetenv PATH # Dangerous!
# Special variables
echo $0 # Shell name
echo $ # Process ID
echo $? # Exit status of last command
echo $#argv # Number of arguments
echo $argv[*] # All argumentsString Operations
# String concatenation
set first = "Hello"
set second = "World"
set combined = "$first, $second!"
echo $combined # Hello, World!
# String length (tcsh)
set string = "Hello, World!"
echo $%string # Length: 13
# Substring operations (limited in csh)
set filename = "document.txt"
set basename = $filename:r # Remove extension: document
set extension = $filename:e # Get extension: txt
set dirname = $filename:h # Get directory (if path)
set tail = $filename:t # Get filename (if path)
# Case conversion (tcsh)
set upper = $string:u # Uppercase
set lower = $string:l # LowercaseCommand Substitution
# Command substitution using backticks
set current_date = `date`
set file_count = `ls|wc -l`
set user_home = `eval echo ~$USER`
# Using command substitution in expressions
echo "Today is `date +%A`"
set files = (`ls *.txt`)
# Nested command substitution
set day_of_week = `date +%A`
echo "Today is $day_of_week, `date +%B` `date +%d`"Control Structures
Conditional Statements
# if-then-else
if ($age >`` 18) then
echo "Adult"
else if ($age == 18) then
echo "Just turned adult"
else
echo "Minor"
endif
# String comparisons
if ("$name" == "John") then
echo "Hello John"
endif
if ("$name" != "John") then
echo "Not John"
endif
# File tests
if (-f "file.txt") then
echo "File exists"
endif
if (-d "directory") then
echo "Directory exists"
endif
if (-r "file.txt") then
echo "File is readable"
endif
if (-w "file.txt") then
echo "File is writable"
endif
if (-x "script.sh") then
echo "File is executable"
endif
# Logical operators
if ($age > 18 && $age ``< 65) then
echo "Working age"
endif
if ($status == 0||$force == "true") then
echo "Proceeding"
endif
if (! -f "file.txt") then
echo "File does not exist"
endifSwitch Statements
# switch statement
switch ($variable)
case pattern1:
echo "Matched pattern1"
breaksw
case pattern2:
case pattern3:
echo "Matched pattern2 or pattern3"
breaksw
default:
echo "No pattern matched"
breaksw
endsw
# Switch with file extensions
switch ($filename)
case *.txt:
echo "Text file"
breaksw
case *.jpg:
case *.png:
case *.gif:
echo "Image file"
breaksw
case *.sh:
echo "Shell script"
breaksw
default:
echo "Unknown file type"
breaksw
endswLoops
# foreach loop
foreach item (apple banana orange)
echo "Fruit: $item"
end
# foreach with array variable
set files = (*.txt)
foreach file ($files)
echo "Processing: $file"
end
# foreach with command substitution
foreach user (`cat users.txt`)
echo "User: $user"
end
# while loop
set counter = 1
while ($counter <= 10)
echo "Counter: $counter"
@ counter++
end
# while loop with file reading
set line = ""
while (1)
set line = $<
if ($line == "") break
echo "Line: $line"
end
# Nested loops
foreach dir (/usr /opt /var)
foreach file ($dir/*)
if (-f $file) then
echo "File: $file"
endif
end
endArithmetic Operations
Arithmetic with @ Command
# Basic arithmetic
@ result = 5 + 3 # 8
@ result = 10 - 4 # 6
@ result = 6 * 7 # 42
@ result = 20 / 4 # 5
@ result = 17 % 5 # 2 (modulo)
# Arithmetic with variables
set num1 = 10
set num2 = 5
@ sum = $num1 + $num2 # 15
@ product = $num1 * $num2 # 50
# Increment and decrement
set counter = 0
@ counter++ # Increment
@ counter-- # Decrement
@ counter += 5 # Add and assign
@ counter -= 3 # Subtract and assign
# Complex expressions
@ result = ($num1 + $num2) * 2
@ result = $num1 ** 2 # Exponentiation (tcsh)
# Comparison operations
@ is_greater = ($num1 >`` $num2) # Returns 1 if true, 0 if false
if ($is_greater) then
echo "num1 is greater than num2"
endifExternal Arithmetic Tools
# Using expr for complex calculations
set result = `expr 5 + 3`
set result = `expr $num1 \* $num2` # Note: * must be escaped
# Using bc for floating point
set result = `echo "scale=2; 10/3"|bc`
set result = `echo "scale=4; sqrt(16)"|bc -l`
# Using awk for calculations
set result = `awk "BEGIN \\{print 10/3\\}"`Aliases and History
Alias Management
# Simple aliases
alias ll 'ls -l'
alias la 'ls -la'
alias h 'history'
alias .. 'cd ..'
alias ... 'cd ../..'
# Aliases with arguments
alias rm 'rm -i' # Interactive removal
alias cp 'cp -i' # Interactive copy
alias mv 'mv -i' # Interactive move
# Complex aliases
alias lsd 'ls -l|grep "^d"' # List only directories
alias psg 'ps aux|grep' # Process search
# Conditional aliases
if (-f /usr/bin/vim) then
alias vi vim
endif
# List aliases
alias # Show all aliases
alias ll # Show specific alias
# Remove aliases
unalias ll
unalias * # Remove all aliasesHistory Management
# History configuration
set history = 1000 # Number of commands to remember
set savehist = 1000 # Number of commands to save to file
# History commands
history # Show all history
history 10 # Show last 10 commands
history -r # Read history from file
history -w # Write history to file
# History expansion
!! # Previous command
!n # Command number n
!string # Last command starting with string
!?string # Last command containing string
^old^new # Replace old with new in previous command
# History modifiers
!:0 # Command name only
!:1 # First argument
!:$ # Last argument
!:* # All arguments
!:1-3 # Arguments 1 through 3
# Examples
echo !$ # Echo last argument of previous command
cp file.txt !$.bak # Copy file with .bak extensionJob Control and Process Management
Job Control
# Background jobs
command & # Run command in background
jobs # List active jobs
fg %1 # Bring job 1 to foreground
bg %1 # Send job 1 to background
kill %1 # Kill job 1
# Job control signals
# Ctrl+C: Interrupt (SIGINT)
# Ctrl+Z: Suspend (SIGTSTP)
# Ctrl+\: Quit (SIGQUIT)
# Process management
ps # Show current processes
ps aux # Show all processes
kill PID # Terminate process
kill -9 PID # Force kill process
killall process_name # Kill all processes by name
# Nohup equivalent
nohup command & # Run command immune to hangupsProcess Information
# Process variables
echo $ # Current shell PID
echo $! # PID of last background job
# Process status
echo $? # Exit status of last command
echo $status # Same as $? in csh
# Wait for processes
wait # Wait for all background jobs
wait %1 # Wait for specific jobInput/Output and Redirection
Basic I/O Redirection
# Output redirection
command > file.txt # Redirect stdout to file
command >> file.txt # Append stdout to file
command >& file.txt # Redirect both stdout and stderr
command >>& file.txt # Append both stdout and stderr
# Input redirection
command < input.txt # Read input from file
sort < unsorted.txt > sorted.txt
# Pipes
ls -l|grep "txt" # Pipe output to grep
ps aux|grep "process"|wc -l # Count matching processes
# Here documents (limited support)
cat << EOF
This is a here document
Variables like $HOME are expanded
EOFAdvanced I/O Features
# Noclobber option
set noclobber # Prevent overwriting files
command >! file.txt # Force overwrite with noclobber set
# Tee equivalent
command|tee file.txt # Write to file and stdout
# Error redirection
command >& /dev/null # Redirect both stdout and stderr to null
(command > output.txt) >& error.log # Separate stdout and stderrBuilt-in Commands and Features
Essential Built-ins
# echo command
echo "Simple message"
echo -n "No newline" # tcsh only
# printf (tcsh only)
printf "%s: %d\n" "Count" 42
printf "%-10s %5d\n" "Name" 123
# set and setenv
set var = value # Local variable
setenv VAR value # Environment variable
# which and where
which command # Show command location
where command # Show all command locations (tcsh)
# Directory operations
cd directory # Change directory
pushd directory # Push directory onto stack
popd # Pop directory from stack
dirs # Show directory stack
# File operations
ls -l # List files
cp source dest # Copy files
mv old new # Move/rename files
rm file # Remove files
mkdir directory # Create directory
rmdir directory # Remove empty directory
```### Recursos Específicos do tcsh
```bash
# Command completion
set complete = enhance # Enhanced completion
set autolist # Automatically list completions
# Spelling correction
set correct = cmd # Correct commands
set correct = complete # Correct completions
set correct = all # Correct everything
# File completion
set filec # Enable filename completion
# Auto-logout
set autologout = 60 # Auto-logout after 60 minutes
# Watch for logins
set watch = (any any) # Watch for any user login
set who = "%n has %a %l from %M at %t." # Login message format
```## Configuração e Personalização
```bash
# Simple prompts
set prompt = '%n@%m:%c$ ' # user@host:dir$
set prompt = '% ' # Simple %
set prompt = '\! % ' # History number %
# Prompt escape sequences
# %n - Username
# %m - Hostname
# %c - Current directory (basename)
# %C - Current directory (full path)
# %/ - Current directory (full path)
# %~ - Current directory (with ~ substitution)
# %t - Time (12-hour)
# %T - Time (24-hour)
# %p - Time (AM/PM)
# %d - Day of week
# %D - Date
# %w - Month
# %W - Year
# %! - History number
# %# - # if root, % otherwise
# Advanced prompt with colors (tcsh)
set prompt = '%\\\\{\033[1;32m%\\\\}%n@%m%\\\\{\033[0m%\\\\}:%\\\\{\033[1;34m%\\\\}%c%\\\\{\033[0m%\\\\}$ '
# Multi-line prompt
set prompt = '%n@%m:%c\
$ '
# Conditional prompt
if ($uid == 0) then
set prompt = 'root@%m:%c# '
else
set prompt = '%n@%m:%c$ '
endif
```### Personalização do Prompt
```bash
# Path management
set path = (/usr/local/bin /usr/bin /bin)
set path = ($path /opt/bin) # Append to path
# Environment variables
setenv EDITOR vi
setenv PAGER less
setenv BROWSER firefox
setenv LANG en_US.UTF-8
# Platform-specific configuration
switch (`uname`)
case Linux:
setenv LS_COLORS 'di=34:ln=35:so=32:pi=33:ex=31:bd=46;34:cd=43;34:su=41;30:sg=46;30'
breaksw
case Darwin:
setenv LSCOLORS ExFxCxDxBxegedabagacad
breaksw
endsw
# Conditional environment
if (-d "$HOME/.local/bin") then
set path = ($HOME/.local/bin $path)
endif
if ($?DISPLAY) then
setenv BROWSER firefox
else
setenv BROWSER lynx
endif
```### Configuração de Ambiente
```bash
# Important shell options
set noclobber # Prevent file overwriting
set notify # Report job status immediately
set noglob # Disable filename expansion
set ignoreeof # Don't exit on Ctrl+D
# tcsh-specific options
set autolist # List completions automatically
set complete = enhance # Enhanced completion
set correct = cmd # Correct commands
set filec # Filename completion
set histdup = erase # Remove duplicate history entries
set listjobs = long # Long format for job listing
set rmstar # Ask before rm *
```### Opções de Shell
```bash
#!/bin/csh -f
# Script description
# Note: -f flag prevents reading .cshrc
# Variable declarations
set script_name = $0:t
set script_dir = $0:h
set version = "1.0"
# Function equivalent (using goto/label)
goto main
usage:
echo "Usage: $script_name [options] [arguments]"
echo "Options:"
echo " -h Show this help"
echo " -v Show version"
exit 0
version:
echo "$script_name version $version"
exit 0
error:
echo "Error: $error_msg"
exit 1
main:
# Parse arguments
while ($#argv > 0)
switch ($argv[1])
case -h:
goto usage
case -v:
goto version
case -*:
set error_msg = "Unknown option: $argv[1]"
goto error
default:
break
endsw
shift argv
end
# Main script logic
echo "Script execution completed"
exit 0
```## Considerações de Script
```bash
# Use tcsh instead of csh for scripts
#!/bin/tcsh -f
# Always use -f flag to avoid .cshrc interference
#!/bin/csh -f
# Error handling
set error_exit = 0
if (! -f "required_file.txt") then
echo "Error: Required file not found"
set error_exit = 1
endif
if ($error_exit) exit 1
# Input validation
if ($#argv == 0) then
echo "Error: No arguments provided"
exit 1
endif
# Safe variable usage
if ($?variable) then
echo "Variable is set: $variable"
else
echo "Variable is not set"
endif
# Avoid complex scripting in csh
# Use sh/bash for complex scripts
# Use csh/tcsh primarily for interactive use
```### Estrutura de Script
```bash
# csh scripting limitations:
# 1. No functions (use goto/labels instead)
# 2. Limited error handling
# 3. No local variables in "functions"
# 4. Inconsistent syntax
# 5. Poor signal handling
# Example of workaround for function-like behavior
goto main
# "Function" using goto/label
process_file:
set file = $1
if (-f $file) then
echo "Processing $file"
# Process file here
else
echo "File $file not found"
endif
goto return_point
main:
set return_point = main_continue
set argv[1] = "test.txt"
goto process_file
main_continue:
echo "Back in main"
exit 0
```### Melhores Práticas para Scripts csh
```bash
# Good for:
# - Interactive shell use
# - Simple automation tasks
# - Users familiar with C-like syntax
# - Legacy system compatibility
# Not recommended for:
# - Complex scripting (use bash/sh instead)
# - Portable scripts
# - Production automation
# - Error-critical applications
# Migration example from csh to bash
# csh version:
# if ($status == 0) then
# echo "Success"
# endif
# bash equivalent:
# if [ $? -eq 0 ]; then
# echo "Success"
# fi
```## Limitações e Alternativas
```bash
# Running bash scripts from csh
bash script.sh
# Converting csh variables for bash
setenv BASH_VAR $csh_var
bash -c 'echo $BASH_VAR'
# Calling csh from bash
csh -c 'echo $csh_variable'
# Mixed environment
# Use bash for scripting, csh for interactive
exec bash script.sh # Execute bash script
exec tcsh # Return to tcsh
```### Limitações Conhecidas