To verify if programmatic EOF behaves like manual Ctrl+D:

# Test case using cat
{ 
  echo "First line";
  printf '\004';
  echo "This shouldn't appear";
} | cat

# Expected output:
# First line

Programmatic EOF is useful in:

• Automated testing of interactive scripts
• Batch processing with heredoc
• Non-interactive session control

# Example: Automated script input
{
  echo "username";
  echo "password";
  printf '\004';
} | interactive_login_script

Be aware that some programs might handle EOF differently:

• Multiple EOFs might be required for some applications
• Buffering might affect immediate processing
• Terminal settings can modify EOF behavior

In Unix-like systems, EOF (End-of-File) is represented by ASCII code 4 (EOT - End of Transmission), not -1. The Ctrl+D key combination sends this character to indicate the end of input to a program.

Here are several ways to simulate Ctrl+D behavior in bash scripts:

# Method 1: Using printf with octal escape
printf '\004'

# Method 2: Using ANSI-C quoting
echo $'\x04'

# Method 3: Using actual Ctrl+D character (in VIM: Ctrl+V followed by Ctrl+D)
echo "^D"

Let's create a test script to verify if programmatic EOF works like manual Ctrl+D:

#!/bin/bash

# Test script that reads until EOF
echo "Testing EOF behavior..."
count=0
while read -r line; do
    ((count++))
    echo "Read line $count: $line"
done

echo "Total lines read: $count"

Now let's feed it with programmatic EOF:

{
    echo "First line"
    printf '\004'
    echo "This shouldn't appear"
} | ./test_script.sh

1. The EOF character must be at the start of a line to be recognized (same as Ctrl+D behavior)

2. Some programs might handle EOF differently - test with your specific use case

3. In pipes, EOF handling can vary depending on how the receiving program processes input

For feeding input to programs that expect EOF, you might consider:

# Using here-document with EOF marker
some_program <