Lecture 8: Shell ( ch 5)

Lecture 8: Shell (ch 5) IT244 - Introduction to Linux / Unix Instructor: Bo Sheng

Redirection • Redirecting standard output ( > ) command [arguments] > filename

Redirection • Redirecting standard output ( > ) • Examples • echo hello world > hello • cat > sample • cat hello > sample • cat days months > sample

Redirection • Redirecting standard output ( > ) • Examples • ls > filelist • Append (>>) • echo append >> hello

Redirection • Redirecting standard input ( < ) command [arguments] < filename

Pipes and Redirection command1 [arguments] | command2 [arguments] command1 [arguments] > temp command2[arguments] < temp rm temp

Some New Utilities • Translate (tr) • trabc ABC • trhld xyz < hello • tr “[A-Z]” “[a-z]” linux • Examples • cat month colors.1|tr “[A-Z]” “[a-z]” | sort

Some New Utilities • Split directions (tee) • tee filename • ls –l | tee filelist • cat colors.1 | tee file1 > file2 • grep e colors.1 | tee /dev/pts/1 | sort

More Examples • Use tr to replace or delete characters • echo “this is a test” > test • wc -c test • tr -d “ ” < test | wc –c • Control characters count • echo hi(CTRL+V, CTRL+A) > hello • wc -c hello

More Examples • Redirection • echo “***” >> hello • Insert a line before the first line • echo “***” > temp • cat temp hello > hello.new • mvhello.new hello • cat hello >> temp • mv temp hello • cat temp hello > hello ?

Filename Generation/Wildcards • “*” and “?” • “?” : single character • “*” : any number of characters (including 0) • ls colors.? • echo col* • ls hello*

Filename Generation/Wildcards • Examples • echo ????? • echo ~/.* • cat hello*

Filename Generation/Wildcards • “[]” for range • echo [aeiou]* • cat colors.[135] • echo [a-z]* • echo *[a-l] • “^” for “not” • echo *[^a-z] • echo [^a-o]*

Filename Generation/Wildcards • Shell expands ambiguous filenames • ls hello? • ls hello\? The shell searches for matching filenames: hello1, hello2 hello1, hello2 ls hello? shell ls

Execute Commands • Foreground and background jobs • cp ~shengbo/it244/exetest . • ./exetest(CTRL+C to terminate) • ./exetest & (running in background) • jobs

Execute Commands • Foreground and background jobs • One foreground in a terminal • Only foreground gets input from keyboard • Multitasking

Execute Commands • Job number / PID number Job number Process ID

Execute Commands • Suspend a foreground job • exetest • CTRL+Z • jobs • Different from a running background job

Execute Commands • Resume a suspended job • In the background • bg [%job_number] • In the foreground • fg [%job_number] • Bring background job to foreground

Execute Commands • Abort a job • Foreground • CTRL+C • Background • kill process_ID • tail –f hello &

Lecture 8: Shell ( ch 5)