1. CIRC Summer School 2016 Baowei Liu
Bash Scripting
CIRC Summer School 2016
Baowei Liu

2. Day 3 Examples ssh to bluehive cd your directory for this class
./shareFiles.sh Day3

3. Stdin, stdout and stderr
File descriptor(FD): a handle to access a file
Stdin: standard input stream (e.g. keyboard) –FD:0
Stdout: standard output stream (e.g. monitor) –FD:1
Stderr: standard error output stream (usually also on monitor) ) –FD:2

4. I/O Redirection: Redirecting to a file
Redirect between files including the three file descriptors, stdin, stdout and stder
Redirecting output: date > file
Appending redirecting output: date >> file
Redirecting input: Command < input

5. I/O Redirection: Pipes
Pipes connect the standard output of one command to the standard input of another with the pipe symbol |.
command1 | command2

6. Filename Expansion / Globbing
Expanding filenames containing special characters
Wild cards * ?
Square brackets [set]: “-”
Special characters: ! (other than)
Escaping backslash: protect a subsequent special character

7. grep
grep: search for matches to a pattern in a file and print the matched line to stdout
grep Pattern file
Pattern could be simple strings or regular expressions

8. Regular Expression Regular Expression: globbing pattern used for text
. : Equivalent to ? in filename expansion
.*: any string. Equivalent to * in filename expansion
* : zero or more times, a* will match a,aa,…but not ab
^: starting with, ^ab
$: ending with, ab$

9. Regular Expression
[]: “-”
\< \>: exact word

10. sed and Regular Expressions
Stream editor for parses and transform text
sed ‘s/abc/xyz’ File: All occurrences
sed ‘5,10s/abc/xyz’ File: range, specified lines
Sed ‘0~2 s/abc/xyz/’ File: Every other line starting 0 or even lines

11. Project
Write a Bash script to black out sensitive information buried in the files under files/
./shareFiles.sh finalProject
Key tech: editor, chmod, command substitution, for loop, echo, sed, regular expression, i/o redirection