Bash: Is there a builtin command to write lines?

stf92 · 07-26-2012, 05:19 AM

Hi:

The read command reads one line of text. Is there a builtin command to write lines? prinf write a line and I can use an empty format string. But it realy writes FORMATTED lines. In C there is puts, and all the other puts besides printf. So may be in bash there is something like it.

GNU bash, version 3.1.17

TobiSGD · 07-26-2012, 05:24 AM

Have a look at the echo command.

stf92 · 07-26-2012, 05:28 AM

Thanks a lot. I would never had guess it.

kauuttt · 07-26-2012, 05:32 AM

Maybe you can have a look at the printf command (for BASH) too!

stf92 · 07-26-2012, 06:03 AM

By the way, consider

Code:

#!/bin/sh

while read line ;
do
echo $line
done<foo >jose

If for each line that is read I want to output it, how do I do? Modifying the echo line, that is 'echo $line > some_file won't do.

414N · 07-26-2012, 06:18 AM

Quote:

Originally Posted by stf92

By the way, consider

Code:

#!/bin/sh

while read line ;
do
echo $line
done<foo >jose

If for each line that is read I want to output it, how do I do? Modifying the echo line, that is 'echo $line > some_file won't do.

Code:

cp foo jose

Jokes aside, do you want to append every single line read inside the while cycle to the same output file? You should use the ">>" operator instead of the ">", which overwrites every time the output file.

NevemTeve · 07-26-2012, 06:18 AM

Or:

Code:

while read line ;
do
    printf "%s\n" "$line"
done<foo >jose

stf92 · 07-26-2012, 06:22 AM

Thanks. I did it the other way:

Code:

echo $line >> jose

But I tried your solution, only that with only one '>' in the echo sentence.

stf92 · 07-26-2012, 06:30 AM

Quote:

Originally Posted by 414N

Code:

cp foo jose

Jokes aside, do you want to append every single line read inside the while cycle to the same output file? You should use the ">>" operator instead of the ">", which overwrites every time the output file.

Its only a skeleton for aa larger script. And is it possible to locate a given substring within line with only buitins? And with an external command?

414N · 07-26-2012, 06:43 AM

You can use the case statement, which can apply some kind of pattern matching, like:

Code:

case $VAR in
foo?foo)
	echo "fooXfoo found"
	;;
*bar*)
	echo "bar found inside the string"
	;;
esac

If case can't help you, you can try grep, sed or awk.

stf92 · 07-26-2012, 06:49 AM

Case is then all I need. Thanks a lot.

414N · 07-26-2012, 06:52 AM

You're welcome

Please mark the thread as solved if the original issue is no more.

stf92 · 07-26-2012, 07:09 AM

I do not understand the case syntax. I want to do (pseudocode)

Code:

if (PERFORMER in $line) then
{
continue
else
echo $line
}

How should I do it with case? Is there an else case in the case construction?

All's well that ends well. Now I understand it.

NevemTeve · 07-26-2012, 07:18 AM

Code:

grep -v -- "PERFOMER" <inputfile | while read line; do
done

414N · 07-26-2012, 07:22 AM

Is PERFORMER the literal substring you're searching in every line?
If so:

Code:

case $line in
*PERFORMER*)
	continue
	;;
*)
	echo $line
	;;
esac

The patterns you can specify in a case statement (those before the 'close bracket' ')') can use wildcards such as * (0 or more characters) or ? (0 or 1 character) or + (1 or more characters).
In this case, we first look if $line contains PERFORMER in a non-specified position (* before and after it means that there can be 0 or more chars before and after it) and, if so, we continue.
If there was no match with the first pattern, than case tries to match $line with the second one (which matches everything) and proceeds to echo the line.
Hope this is clear enough to understand.