UNIX for Dummies Questions & Answers

Hi,

When I use "read" to parse the sftp command sent via ptty, I ran into a very mysterious case below:
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In Unix, the command ‘quit' is lost.
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Fri 13Apr12 15:42:47GMT-sftp_send_command: SENT [quit^M]
Fri 13Apr12 15:42:47GMT-sftp_read_resp_line: Parse buffer=quit^M --> Command sent correctly
Fri 13Apr12 15:42:47GMT-sftp_read_resp_line: Parse buffer char ptr=^M --> only parse the last character.
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In Linux, everything working fine.
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Fri 13Apr12 07:59:29GMT-sftp_send_command: SENT [quit^M]
Fri 13Apr12 07:59:29GMT-sftp_read_resp_line: Parse buffer=quit^M
Fri 13Apr12 07:59:29GMT-sftp_read_resp_line: Parse buffer char ptr=q
Fri 13Apr12 07:59:29GMT-sftp_read_resp_line: Parse buffer char ptr=u
Fri 13Apr12 07:59:29GMT-sftp_read_resp_line: Parse buffer char ptr=i
Fri 13Apr12 07:59:29GMT-sftp_read_resp_line: Parse buffer char ptr=t
Fri 13Apr12 07:59:29GMT-sftp_read_resp_line: Parse buffer char ptr=^M
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The following codes are used to parse the sftp command, what's going wrong in UNIX system? How to correct it?
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ret = select (sftp->msfds[MASTER_FD]+1, &fd, NULL, NULL, &tv);
...
/* read byte by byte to catch the '\n' */
nread = read (sftp->msfds[MASTER_FD], (void *) ptr, 1); -> same in Unix and Linux systems.
...
Really appreciate any help.

Best regards,
HK

Exactly which OSs are you talking about?

The Unix is on 5.10 Generic_137111-06 sun4v sparc. and The Linux is on 2.6.18-238.1.1.el5 #1 SMP x86_64 x86_64 x86_64 GNU/Linux