Consider having the results from the pipe:
find .
Now I would like to access in the second command behind the pipe what is actually piped (inpu
Short answer: You can print each file twice using sed:
find . | sed 's/.*/& &/'
Sed can edit lines as they are inputted. The above command says s
(substitute) .*
(the entire line) & &
(with itself, twice).
Longer answer: When you pipe one program into another, you're connecting the first program's standard output stream to the second program's standard input stream. Anything the first program prints will be treated as input for the second program.
Unfortunately for your example, the input doesn't come in line-by-line chunks that map nicely to a hypothetical $args
variable. It comes in a big monolithic stream. If you want to print each line of the stream twice, you can use sed (which is a Stream EDitor), but it's just doing line-by-line replacements.
Ignoring the possibility that file names contain newlines, you can use sed
as pringley suggests in his answer, or you can create a while
loop with the read
command:
find . |
while read -r line
do
echo "$line$line"
done
(The -r
is for 'raw' input; it stops the shell expanding backslash escape sequences in the input, and is a standard POSIX feature of the read
command in the shell.)
Since you mention bash
, you can avoid problems with newlines in the file names by using the find . -print0
option to terminate each name by a null byte ('\0'
in C) instead of a newline, and then use:
find . -print0 |
while read -r -d '' line
do
echo "X${line}${line}X"
done
The -d ''
replaces the normal newline delimiter with the first character of the string argument, but the string is empty so the first character is the only character is a null byte.
There isn't an easy way (nor, as far as I know, a hard way) to use a for
loop along the lines of:
for line in $(find .)
do
echo "X${line}${line}X"
done
which works reliably for names with spaces, or newlines in them.
Often, you may want to use the xargs
command. This reads standard input and creates a command line using what's read from standard input as arguments to the command.
find . | xargs wc -l
Or, with newline and space safety (by default, xargs
splits arguments at spaces, tabs and newlines):
find . -type f -print0 | xargs -0 wc -l
There are a lot of options you can apply to xargs
— especially the GNU version.
However, you also have options to find
that largely make xargs
redundant:
find . -type f -exec wc -l {} +
which does basically the same job as the find . -print0 | xargs -0 wc -l
command. One difference is that if there are no files in the output from find
, then using -exec
won't execute wc
at all, whereas by default, xargs
will execute it once (with no file name argument; this is for POSIX compliance). With GNU xargs
, you can use -r
or --no-run-if-empty
to stop that happening. Mac OS X xargs
seems to do that anyway.
find . | xargs -I{} printf "%s%s\n" {} {}