Download echo, cat, seq, wc, head, tail, less, more

echo, cat, seq, wc, head, tail, less, more
‣  echo writes command line arguments to stdout
UNIX> echo HELLO THERE
HELLO THERE
‣  Use double quotes for complex strings
UNIX> echo “> < | 2> >> 2>> ! * #”
> < | 2> >> 2>> ! * #
‣  cat prints stdin to stdout
UNIX> cat
I am typing this message <ENTER>
I am typing this message
<CTRL-C>
UNIX>
‣  cat concatenates file(s) and prints to stdout
‣  File(s) specified as command line arguments
UNIX> echo “line 1” > input1.txt
UNIX> echo “line 2” > input2.txt
UNIX> cat input1.txt input2.txt
line 1
line 2
‣  seq outputs a sequence of numbers to stdout
‣  Single command line argument: seq to
–  starts at 1
–  increments by +1
UNIX> seq 3
1
2
3
‣  two command line arguments: seq from to
‣  default increment is +1
UNIX> seq -1 1
-1
0
1
UNIX> seq 2.5 3.5
2.5
3.5
‣  three command line arguments: seq from incr to
UNIX> seq 2 -1 -2
2
1
0
-1
-2
‣  three command line arguments: seq from incr to
UNIX> seq 0 0.3 1
0.0
0.3
0.6
0.9
‣  wc displays the number of lines, words, and
characters in file(s)
‣  wc output:
num_lines
num_words
num_chars
‣  wc takes command line argument(s) or stdin
[file]
UNIX> echo HELLO THERE > input1.txt
UNIX> echo THIS IS ANOTHER FILE > input2.txt
UNIX> wc input1.txt input2.txt
1 2 12 input.txt
1 4 21 input2.txt
2 6 33 total
‣  -l for lines only (lower case L)
‣  -w for words only
‣  -c for characters only
UNIX> echo HELLO THERE | wc –c
12
UNIX> echo HELLO THERE | wc –c –w
2
12
UNIX> echo HELLO THERE | wc
1
2
12
UNIX> seq -74.5 0.01 64.47 | wc
13898 13898 88839
‣  head prints the first line(s) of a file
‣  head accepts a command line argument or stdin
‣  by default, head prints the first 10 lines
UNIX> seq 100 | head
1
…
10
‣  –n command line option specifies number of lines
UNIX> seq 100 > file.txt
UNIX> head –n 2 file.txt
1
2
UNIX> seq 100 | head –n 1
1
‣  tail prints the last line(s) of a file
‣  tail accepts a command line argument or stdin
‣  by default, tail prints the last 10 lines
UNIX> seq 100 | tail
91
…
100
‣  –n command line option specifies number of lines
UNIX> seq 100 > file.txt
UNIX> tail –n 2 file.txt
99
100
UNIX> seq 100 | tail –n 1
100
‣  Use head and tail to print specific lines:
UNIX> seq 100 | head -n 50 | tail -n 5
46
47
48
49
50
‣  less displays a file in read-only mode
‣  Accepts command line argument(s) or stdin
‣  Great way to (quickly) view file contents
‣  Navigate with up and down arrows
‣  ‘q’ to quit
UNIX> less file.txt
UNIX> seq 1000 | less
‣  more displays a file in read-only mode
‣  Accepts command line argument(s) or stdin
‣  Great way to (quickly) view file contents
‣  Page down with spacebar (no arrows)
‣  ‘q’ to quit
UNIX> more file.txt
UNIX> seq 1000 | more
‣  A joke amongst Linux users…
‣  Practice using output commands
http://eecs.mines.edu/Courses/csci274/
Assignments/9_output.html