Read the inputs from a file and save the output to another file in shell script

Question

Everyone, I have created a script for getting time difference between two different epoch time value.

Currently my script reads two value named a and b and gives the output of time different as shown below,

Input:

Enter the TIME A
12345567787

Enter the TIME B
12356777897

Output:

-00.36 hours

How I can read A and B value from a single text file named time.txt and save the time different output to another file "timediff.txt".

How my input file "time.txt" looks like.

    A              B
123456789       123456755
123445567       123434657
128765809       141536478
127576589       163636376
125364758       132653758
.                .
.                .
.                .
n                n

What i'm expecting to output file timediff.txt looks like,

 A                B                    output
123456789    123456755   03.00
123445567    123434657   09.00
128765809    141536478   04:44
127576589    163636376   08:22
125364758    132653758   05:13
.            .           .
.            .           .
.            .           .
n            n           n

Any tutorial on shell scripting should show how to read from a file. — Barmar
– Barmar, Commented Oct 4, 2017 at 20:51

Barmar · Accepted Answer · 2017-10-04 20:52:50Z

1

Use a while loop that uses the read built-in. Redirect the input from the input file, and the output to the output file.

while read a b
do
    # your code here
done < time.txt > timediff.txt

answered Oct 4, 2017 at 20:52

Barmar

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2 Comments

Prabakaran Venkatesh Over a year ago

Configuring a System Event: To set SecureSphere to send syslog messages based on the CEF standard when a system event occurs: 1 Define a new Action Set and configure the parameters as follows: Name: The action set name, for example, system_syslog. Syslog Host: The IP or host name of the Syslog server. Syslog Log Level: The Syslog log level. Message: The CEF message for a system event. CEF:0|ImpervaInc.|SecureSphere|6.0|${Event.eventType}|${Event.message}|${Event.severity.displayName}|suser=${Event.username} rt=# (${Event.createTime}) cat=SystemEvent

Barmar Over a year ago

@PrabakaranVenkatesh I don't understand what your comment has to do with my answer.

William Pursell · Accepted Answer · 2017-10-04 20:52:54Z

0

It would be much cleaner if your script were less verbose and took its operands from arguments rather than reading them from stdin, but (assuming your prompts are going to stderr) you can do:

while read a b; do 
  printf "$a\t$b\t%s\n" "$(printf "$a\n$b\n" | myscript)"
done < time.txt > timediff.txt

If your prompts are intermingled with your ouptut, I strongly suggest you change your script (conveniently called myscript above) to have a more reasonable usage.

answered Oct 4, 2017 at 20:52

William Pursell

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1 Comment

glenn jackman Over a year ago

Since the first argument of printf is the format string, you are susceptible to variables containing the % character. Safer is printf "%s\n%s\n" "$a" "$b"

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