STDOUT vs STDERR

[gotmikhail]

Is there any particular reason why all output is directed to STDERR?

Or, is there a chance I'm doing something wrong on my machine. Yesterday I downloaded the latest, compiled, and installed with the same results on Fedora 29

[J. Riesmeier]

It would be helpful if you could provide an example that shows what you did or tried to do, e.g. are your talking about the log output, the console output of tools such as dcmdump...?

[gotmikhail]

I could be going about this the wrong way, but here's a simple example:

Let's run `findscu` from terminal (anonymized, so bogus IPs, etc, ignore) in verbose:

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findscu -S -v -k 0010,0010 -k 0010,0020 -k 0010,0030 -k 0008,0020 -k 0008,0030 -k 0008,0061=SR -k 0008,0050=ABCDE -k 0020,000d -aec OTHERAE xx.xx.xx.xx 104 -aet MYAET 

Gives us:

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I: Requesting Association
I: Association Accepted (Max Send PDV: 16340)
I: Sending Find Request (MsgID 1)
I: Request Identifiers:
I: 
I: # Dicom-Data-Set
I: # Used TransferSyntax: Little Endian Explicit
I: (0008,0020) DA (no value available)                     #   0, 0 StudyDate
I: (0008,0030) TM (no value available)                     #   0, 0 StudyTime
I: (0008,0050) SH [ABCDE]                              #  10, 1 AccessionNumber
I: (0008,0052) CS [STUDY]                                  #   6, 1 QueryRetrieveLevel
I: (0008,0061) CS [SR]                                     #   2, 1 ModalitiesInStudy
I: (0010,0010) PN (no value available)                     #   0, 0 PatientName
I: (0010,0020) LO (no value available)                     #   0, 0 PatientID
I: (0010,0030) DA (no value available)                     #   0, 0 PatientBirthDate
I: (0020,000d) UI (no value available)                     #   0, 0 StudyInstanceUID
I: 
I: ---------------------------
I: Find Response: 1 (Pending)
I: 
I: # Dicom-Data-Set
I: # Used TransferSyntax: Little Endian Implicit
I: (0008,0005) CS [ISO_IR 100]                             #  10, 1 SpecificCharacterSet
I: (0008,0020) DA [20000101]                               #   8, 1 StudyDate
I: (0008,0030) TM [0]                                  #  10, 1 StudyTime
I: (0008,0050) SH [ABCDE]                             #  10, 1 AccessionNumber
I: (0008,0052) CS [STUDY ]                                 #   6, 1 QueryRetrieveLevel
I: (0008,0054) AE [OTHERAET]                         #  14, 1 RetrieveAETitle
I: (0008,0056) CS [ONLINE]                                 #   6, 1 InstanceAvailability
I: (0008,0061) CS [SR]                                     #   2, 1 ModalitiesInStudy
I: (0010,0010) PN [Last^First ]             #  26, 1 PatientName
I: (0010,0020) LO [WXYZ]                                 #   6, 1 PatientID
I: (0010,0030) DA [19000101]                               #   8, 1 PatientBirthDate
I: (0020,000d) UI [1.2.840.xxx]                             #  56, 1 StudyInstanceUID
I: (0088,0130) SH (no value available)                     #   0, 0 StorageMediaFileSetID
I: (0088,0140) UI (no value available)                     #   0, 0 StorageMediaFileSetUID
I: 
I: Received Final Find Response (Success)
I: Releasing Association

No errors, but all output is being sent to STDERR. Route STDERR to `/dev/null`, and you have no output to terminal.

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findscu -S -v -k 0010,0010 -k 0010,0020 -k 0010,0030 -k 0008,0020 -k 0008,0030 -k 0008,0061=SR -k 0008,0050=ABCDE -k 0020,000d -aec OTHERAE xx.xx.xx.xx 104 -aet MYAET 2>/dev/null

No output
Redirect STDOUT & STDERR into their own files,

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findscu -S -v -k 0010,0010 -k 0010,0020 -k 0010,0030 -k 0008,0020 -k 0008,0030 -k 0008,0061=SR -k 0008,0050=ABCDE -k 0020,000d -aec OTHERAE xx.xx.xx.xx 104 -aet MYAET 1> stdout.txt 2>stderr.txt

And all the results are in `stderr.txt`

Results are all the same when not using verbose, but the only difference is the "pre-query" info.

[J. Riesmeier]

In contrast to e.g. dcmdump, findscu has no textual output by default. What you see in the info lines (starting with "I:") is the log output, which is usually directed to stderr/cerr. Of course, you can change this default with an appropriate logger configuration (see "oflog/etc/logger.cfg" for an example).