tee: add --remove-cr option

[Nikos Papaspyrou]

I have implemented an option for tee which is helpful when one wants to
capture the output of a program that uses carriage return characters, to
visualize its progress.  I am attaching the patch.

Motivation: Say we want to use the option "status=progress" for dd, in
order to keep track of the task's progress, but we also want to send
the program's output to a log file:

$ dd if=input of=output bs=64 status=progress |& tee LOG
40273024 bytes (40 MB, 38 MiB) copied, 3 s, 13,4 MB/s
805136+1 records in
805136+1 records out
51528755 bytes (52 MB, 49 MiB) copied, 4,04839 s, 12,7 MB/s

$ hexdump -C LOG
00000000  0d 31 33 32 36 34 34 34  38 20 62 79 74 65 73 20  |.13264448 bytes |
00000010  28 31 33 20 4d 42 2c 20  31 33 20 4d 69 42 29 20  |(13 MB, 13 MiB) |
00000020  63 6f 70 69 65 64 2c 20  31 20 73 2c 20 31 33 2c  |copied, 1 s, 13,|
00000030  33 20 4d 42 2f 73 0d 32  36 37 37 34 35 39 32 20  |3 MB/s.26774592 |
00000040  62 79 74 65 73 20 28 32  37 20 4d 42 2c 20 32 36  |bytes (27 MB, 26|
00000050  20 4d 69 42 29 20 63 6f  70 69 65 64 2c 20 32 20  | MiB) copied, 2 |
00000060  73 2c 20 31 33 2c 34 20  4d 42 2f 73 0d 34 30 32  |s, 13,4 MB/s.402|
00000070  37 33 30 32 34 20 62 79  74 65 73 20 28 34 30 20  |73024 bytes (40 |
00000080  4d 42 2c 20 33 38 20 4d  69 42 29 20 63 6f 70 69  |MB, 38 MiB) copi|
00000090  65 64 2c 20 33 20 73 2c  20 31 33 2c 34 20 4d 42  |ed, 3 s, 13,4 MB|
000000a0  2f 73 0a 38 30 35 31 33  36 2b 31 20 72 65 63 6f  |/s.805136+1 reco|
000000b0  72 64 73 20 69 6e 0a 38  30 35 31 33 36 2b 31 20  |rds in.805136+1 |
000000c0  72 65 63 6f 72 64 73 20  6f 75 74 0a 35 31 35 32  |records out.5152|
000000d0  38 37 35 35 20 62 79 74  65 73 20 28 35 32 20 4d  |8755 bytes (52 M|
000000e0  42 2c 20 34 39 20 4d 69  42 29 20 63 6f 70 69 65  |B, 49 MiB) copie|
000000f0  64 2c 20 34 2c 30 34 38  33 39 20 73 2c 20 31 32  |d, 4,04839 s, 12|
00000100  2c 37 20 4d 42 2f 73 0a                           |,7 MB/s.|
00000108

Notice that the LOG file contains more than can be seen in the standard
output. Three lines were printed with progress information, each starting
with a carriage return character (0d). Only the last one remained and can
be seen in the standard output. This is frustrating if one needs to edit
or otherwise process the LOG file.

With the proposed new option, progress information is shown in the
standard output but is not stored to the LOG file:

$ dd if=input of=output bs=64 status=progress |& tee --remove-cr LOG
40865344 bytes (41 MB, 39 MiB) copied, 3 s, 13,6 MB/s
805136+1 records in
805136+1 records out
51528755 bytes (52 MB, 49 MiB) copied, 4,01799 s, 12,8 MB/s

$ hexdump -C LOG
00000000  34 30 38 36 35 33 34 34  20 62 79 74 65 73 20 28  |40865344 bytes (|
00000010  34 31 20 4d 42 2c 20 33  39 20 4d 69 42 29 20 63  |41 MB, 39 MiB) c|
00000020  6f 70 69 65 64 2c 20 33  20 73 2c 20 31 33 2c 36  |opied, 3 s, 13,6|
00000030  20 4d 42 2f 73 0a 38 30  35 31 33 36 2b 31 20 72  | MB/s.805136+1 r|
00000040  65 63 6f 72 64 73 20 69  6e 0a 38 30 35 31 33 36  |ecords in.805136|
00000050  2b 31 20 72 65 63 6f 72  64 73 20 6f 75 74 0a 35  |+1 records out.5|
00000060  31 35 32 38 37 35 35 20  62 79 74 65 73 20 28 35  |1528755 bytes (5|
00000070  32 20 4d 42 2c 20 34 39  20 4d 69 42 29 20 63 6f  |2 MB, 49 MiB) co|
00000080  70 69 65 64 2c 20 34 2c  30 31 37 39 39 20 73 2c  |pied, 4,01799 s,|
00000090  20 31 32 2c 38 20 4d 42  2f 73 0a                 | 12,8 MB/s.|
0000009b

More specifically, lines ending with carriage return are sent to the
standard output but not to the files.

-- 
Nikolaos Papaspyrou
Software Engineer
nikolaos@google.com

Google Germany GmbH
Erika-Mann-Strasse 33
80636 Muenchen

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tee-remove-cr.patch
Description: Binary data