read a file line by line

Shell Programming and Scripting
1

Hello there,
I have a script that I would like to read a file line by line and launch a function with the entire line as a parameter. I wrote something that reads the file word after word. Can you help me correct it?
Thanks in advance
Santiago

~$ cat test
myfunction() {
    # to make it simple, I just echo the argument
    echo "$1"
}
for line in $(cat "$1"); do
    myfunction $line
done
~$ cat file
Santiago Diez
Something else
Anything   weird
~$ ./test file
Santiago
Diez
Something
else
Anything
weird
2

You don't need a function:

while IFS= read -r; do
  yourfunction "$REPLY"
done<filename
3

Thanks radoulov,
I also wrote this solution thanks to this post found in the forum:

while read line; do
    myfunction "$line"
done < "$1"
4

You've removed some parts of my post, so beware of the following:

$ cat -te file
   $
  Santiago Diez  $
Some\thing else$
Anything   weird$
$
$ while read line; do
>   printf '|%s|\n' "$line"
> done<file
||
|Santiago Diez|
|Something else|
|Anything   weird|
||
$ while IFS= read -r line; do
>   printf '|%s|\n' "$line"
> done<file
|   |
|  Santiago Diez  |
|Some\thing else|
|Anything   weird|
||
5

Hum, yes.
Actually, I'm pretty newbee in shell script. Altough I've been working for several months with it, I never had any proper lecture about that.
So I just took out what I couldn't understand and noticed that it was still working... Until you mentioned the limits.
So if you have time, could you help me on that:
1) I found no help about read's switch r.
2) How can you write IFS= just before read, even without semi-colon to separate the commands? What's the purpose? Does it modify the value of IFS forever or just in the loop?
Thanks in advance
Santiago

6

From the bash builtin help:

$ help read
read: read [-ers] [-u fd] [-t timeout] [-p prompt] [-a array] [-n nchars] [-d delim] [name ...]
...
If the -r option is given, this signifies `raw' input, and
    backslash escaping is disabled.

It's set only for the read call. Consider the following:

while IFS= read; do
  printf '\nread with empty IFS: |%s|\n' "$REPLY"
  read inside<<<"$REPLY"
  printf '\nread inside the loop: |%s|\n\n' "$inside"  
  printf "... so the current IFS is:\n"  
  od -bc<<<"$IFS" 
done<<<"   _x_   "

The output is:

read with empty IFS: |   _x_   |

read inside the loop: |_x_|

... so the current IFS is:
0000000 040 011 012 012
             \t  \n  \n
0000004

The combination space, tab and newline is the default value.

7

neat and clear,
thanks a lot

Actually, I didn't know the existence of function help:

~$ man read
No manual entry for read
8

It's a shell builtin, not an external command.
You will find in it in the bash(or whatever shell supporting that builtin you're using) man pages in the SHELL BUILTIN COMMANDS section.

9

Hi,

under bash the is the "help" command for infos on build-in functions. So

help read

should do the trick.

HTH Chris