Bash Commands - the diff of > and >> # Use I/O Redirection to generate a log file

1. >
# Redirect stdout to a file.
# Creates the file if not present, otherwise overwrites it.

2. >>
# Redirect stdout to a file.
# Creates the file if not present, otherwise appends to it.

3. Usage

&>filename # Redirect both stdout and stderr to file "filename."

# This operator is now functional, as of Bash 4, final release.

1>filename # Redirect stdout to file "filename."

1>>filename # Redirect and append stdout to file "filename."

2>filename # Redirect stderr to file "filename."

2>>filename # Redirect and append stderr to file "filename."

: > filename # Clear the file, create it if not present.

For example:

Write a script that upon invocation shows the time and date, lists all logged-in users, and gives the
system uptime. The script then saves this information to a logfile.

#!/bin/bash

LOGFILE=script.log
ERRORFILE=script.errors

date 1>$LOGFILE
logname 1>>$LOGFILE
uptime 1>>$LOGFILE

bad_command1 2>>$ERRORFILE
bad_command2 2>>$ERRORFILE
bad_command3

date &>$LOGFILE
logname &>>$LOGFILE
uptime &>>$LOGFILE

bad_command4 &>>$LOGFILE

# end of file