Data Streams & Pipes

Pipes and Data Streams..

Eg: mkdir Name_Surname && touch Name_Surname/my_file && echo "Hello" > Name_Surname/my_file && cat Name_Surname/my_file || echo "Something went wrong"

Streams

File Descriptors and Data Redirections.

Syntax	Translation	Logic
`2>&1`	”Redirect stderr (2) to stdout (1)“	Both errors and normal output will appear together.
`1>&2`	”Redirect stdout (1) to stderr (2)“	Force standard messages to be treated as errors.
`&> file`	”Redirect both 1 and 2 to file”	Shortcut for sending all output to a single file.

Task

learn to utilize data streams

Tasks:

create a script that does the following:
asks the user to input a filename
writes the following poem to the file specified by user:

An old silent pond…

A frog jumps into the pond,

splash! Silence again.

Autumn moonlight-

a worm digs silently

into the chestnut.

In the twilight rain

these brilliant-hued hibiscus -

A lovely sunset.

outputs the poem to the terminal
outputs the message “Task finished” to stderr
run your script, specify output as the file to write the poem to, redirect stdout to /dev/null, redirect stderr to stderr file

Self-check:

script returns no output
cat output command returns:

An old silent pond...

A frog jumps into the pond,

splash! Silence again.

Autumn moonlight-

a worm digs silently

into the chestnut.

In the twilight rain

these brilliant-hued hibiscus -

A lovely sunset.

cat stderr command returns:

Task finished

#!/bin/bash

# 1. Ask the user for the filename
read -p "Enter filename: " filename

# 2. Write the poem to the specified file
# Use a Heredoc to send text to the file
cat <<EOF > "$filename"
An old silent pond...
A frog jumps into the pond,
splash! Silence again.
Autumn moonlight-
a worm digs silently
into the chestnut.
In the twilight rain
these brilliant-hued hibiscus -
A lovely sunset.
EOF

# 3. Output the poem to the terminal (stdout)
cat "$filename"

# 4. Output message to stderr
echo "Task finished" >&2