How to use a bash script to repeatedly feed a string into a program?

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You can use a for loop in bash, and pipe the result to your program:

for i in {1..1000}
do 
    echo "My input"
done | ./my_program

Or as one line which can be used directly from the command line:

for i in {1..1000}; do echo "My input"; done | ./my_program

Advanced Bash-Scripting Guide, Using pattern matching to parse arbitrary strings; 10-13. Matching Using export to pass a variable to an embedded awk script; 15-21. Using getopts to Redirecting the output of process substitution into a loop. 24-1. Simple Many times, you will write a script that carries out one particular task. The first� The general idea of Expect and similar tools is to wait for a specified string or pattern in the output of a program, and then feed it whatever input you want. A common example use is to automate login, by "expecting" (i.e. waiting for) the string "ogin:", send the login-name, then expect the string "word:" and send the password.

yes does that.

$: yes 1 10 | head
1 10
1 10
1 10
1 10
1 10
1 10
1 10
1 10
1 10
1 10

So for an infinite input,

yes 1 10 | myProg

Or if you want a limit,

yes 1 10 | head -99999 | myProg

Bash variables and command substitution, However, variables really come into use in more advanced programming, in a situation in which the actual values aren't known before executing a program. or a variable reference is within single-quotes, Bash will interpret the string literally: When we write functions and shell scripts, in which arguments are passed in� I'm relatively new to shell scripting, but have nearly completed a script which makes use of the lftp program.The part of the script I am having trouble with is when I create a long string of commands (separated by ;).

This is an endless loop:

while :; do echo "1 10"; done | consumer

Or a less aggressive version:

while sleep 1; do echo "1 10"; done | consumer

Automatically enter input in command line, show 3 more comments NAME yes - output a string repeatedly until killed SYNOPSIS yes In the shell script you can also use the following trick of spawn, expect and send Okay, this may not be a very elegant solution but if you write your options in a separate file and then pass it as an input to the� 1. Use watch Command. Watch is a Linux command that allows you to execute a command or program periodically and also shows you output on the screen. This means that you will be able to see the program output in time. By default watch re-runs the command/program every 2 seconds. The interval can be easily changed to meet your requirements.

Shell Scripting Part 2: Accepting Inputs and Performing Shell , In the second part, you will learn how accept inputs from the user and process them through in Linux and are used to pass information across processes in the shell. OSTYPE, Holds a string that describes the current OS of the machine used To get the entire list of environment variables in Linux use the env command. Using string comparison operators we can also compare strings in the same manner as when comparing numeric values. Consider the following example: If we were to translate the above knowledge to a simple bash shell script, the script would look as shown below.

Pseudo files for temporary data, I often want to feed relatively short string data (could be several lines though) to commandline programs which accept only input from files (e.g. wdiff) in a repeated� One thing you can do is take an argument from the command line. So, for instance, when you run “script foo” the script will take the name of the first argument (foo): #!/bin/bash echo $1 Here bash will read the command line and echo (print) the first argument — that is, the first string after the command itself.

Bash syntax can sometimes be pretty weird, but using arrays in scripts can be really useful. When a script starts to become more complex than expected, my advice is, however, to switch to a more capable scripting language such as python.

Comments

If you've got the program, then yes "1 10" does the job for an indefinite number of iterations (until you interrupt it, or the process it feeds exits, or …). If you want varying input, life is more interesting.
And NOW I see that Jonathan Leffler offered that solution as a comment two hours ago, lol...
On a Mac, I needed the quotes around the '1 10' — the macOS or BSD variant of yes only echoes its first argument. When I use GNU yes, the quotes aren't needed; it echoes all its arguments on each line with spaces separating them. Just another tiny difference. The GNU processing is sensible.