C2110 UNIX and programming Lesson 10 / Module 1 -1C2110
UNIX and programming
Petr Kulhanek
kulhanek@chemi.muni.cz
National Center for Biomolecular Research, Faculty of Science
Masaryk University, Kamenice 5, CZ-62500 Brno
PS / 2020 Distance form of teaching: Roar3
Lesson 10 / Module 1
C2110 UNIX and programming Lesson 10 / Module 1 -2-
Bash
➢ Redirecting input from a script
C2110 UNIX and programming Lesson 10 / Module 1 -3Redirecting
Input from a Script
Standard input redirection of program my_command from file script.
.......
./my_command << EOF
first line text
the other line text
third line text
EOF
......
mark indicating the end of the entry
(user selects)
end of entry, mark must not be
surrounded by spaces
text, whichforms loaded input
This method of redirection is especially useful in scripts, but it also works on the command line. The
advantage is the expansion of variables in the read text.
C2110 UNIX and programming Lesson 10 / Module 1 -4-
Examples
#!/bin/bash
PHASE=1.2
gnuplot << EOF
plot sin(x+$PHASE)
EOF
#!/bin/bash
for((I=1;I<=10;I++)); do
NAME=`printf "%02d.txt" $I`
cat << EOF > $NAME
Toto je soubor cislo: $I
EOF
done
The highlighted text is sent to standard
input of cat command, the variables are
expanded before sending the input, then
the cat command saves it to $NAME file.
In this way, you can programmatically create scripts
for gnuplot.
The result of commands preceded by
back quotation marks `` is saved into the
variable NAME.
C2110 UNIX and programming Lesson 10 / Module 1 -5Exercise
1
1. Write a script that creates ten files. The file name will be in the format XX.txt where XX
is the file number. If the file number is less than ten, use the 0 character for the first
digit in the name. Each file will contain the following text (X is the file number):
2. Write a script that asks the user for the name of the image file in png format and then
renders the sin(x) function into it.
Automatically created text file
File number is: X