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Top Forums Shell Programming and Scripting ret val of a command in a pipe which is NOT the last one Post 30880 by latze on Tuesday 29th of October 2002 08:22:24 AM
Old 10-29-2002
ret val of a command in a pipe which is NOT the last one

hello dear UNIX gurus ;-)

my problem is one of those i would think that many others should also have had it in the past. but i cannot find any thread or other documentation about it.

inside a ksh script i have a pipe like this:

ksh -c "export LIBPATH=$LD_LIBRARY_PATH; ${Cmd} ${Param} 2>&1 | tee -a ${LogFile}"

now i need to return the return value of ${Cmd} to the caller. as everybody knows, the $? gives me the ret val of the tee call, which is not important here. nevetheless i want to use the tee feature here. many this-style pipes can be usefull.

i have tried workarounds with

[[ ! -r ${LogFile} ]] && touch ${LogFile}
tail -f ${LogFile} &
TAILPID=$!
ksh -c "export LIBPATH=$LD_LIBRARY_PATH; ${Cmd} ${Rest} >> ${LogFile} 2>&1"
RET=$?
sleep 5
kill -9 ${TAILPID} > /dev/null 2>&1

exit ${RET}

but i think there must be a better solution, maybe using file descriptors greater than2. but i did not succeed yet :-(

has anybody an idea?

this would be great

thank you all and bye bye

latze
 

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io_pipe(3)						     Library Functions Manual							io_pipe(3)

NAME
io_pipe - create a Unix pipe SYNTAX
#include <io.h> int io_pipe(int64 pfd[2]); DESCRIPTION
io_pipe creates a new UNIX ``pipe.'' The pipe can receive data and provide data; any bytes written to the pipe can then be read from the pipe in the same order. A pipe is typically stored in an 8192-byte memory buffer; the exact number depends on the UNIX kernel. Bytes are written to the end of the buffer and read from the beginning of the buffer. Once a byte has been read, it is eliminated from the buffer, making space for another byte to be written; readers cannot ``rewind'' a pipe to read old data. Once 8192 bytes have been written to the buffer, the pipe will not be ready for further writing until some of the bytes have been read. Once all the bytes written have been read, the pipe will not be ready for further reading until more bytes are written. io_pipe sets d[0] to the number of a new descriptor reading from the pipe, and sets d[1] to the number of a new descriptor writing to the pipe. It then returns 1 to indicate success. If something goes wrong, io_pipe returns 0, setting errno to indicate the error; in this case it frees any memory that it allocated for the new pipe, and it leaves d alone. SEE ALSO
io_readfile(3), io_createfile(3), io_socketpair(3) io_pipe(3)
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