Grep shows a bug, if it processes a text file with at least one embedded 0 (ASCII zero) character after byte 32768. Grep stops with the error message "Binary file testfile.txt matches" and exit code 0. The error message is written to standard output. Any line after the 0 character is silently ignored in output.
Environment: - grep-2.25 - no patches, no "configure" options - openSUSE Tumbleweed 20160611 x86_64; glibc 2.23; libpcre 8.38 I saw this bug first, as I tried to filter out a line of the MySQL backup utility "mysqldump". Because grep stopped at the 0 character, the backups where incomplete. # mysqldump --all-databases | grep -v '^-- Dump completed on' [... around 240 lines of SQL output ...] LOCK TABLES `PartTable` WRITE; /*!40000 ALTER TABLE `PartTable` DISABLE KEYS */; Binary file (standard input) matches mysqldump: Got errno 32 on write I found that the mysqldump output contains 0 characters in table PartTable. I wrote the following test script, which shows the bug without a dependency to MySQL: -------------------------------------------------------- #!/bin/bash testfile="testfile.txt" # write a text file large enough (16384 lines is # the minimum number for this test case) for((i=1;i<=16384;i++)) do echo "A"; done > $testfile # write a zero byte echo -e '\0' >> $testfile # write an end line echo -e 'A ... the end' >> $testfile # verify the file contents ls -l $testfile tail -n 10 $testfile # use 'grep' to find all lines with the string "A" grep "A" $testfile # the last line is missing, the output ends with # "Binary file testfile.txt matches" # check the exit code echo "Exit code of grep:" $? -------------------------------------------------------- The last line "A ... the end" is missing in output of grep. The exit code is 0: # ./null-bug-testcase.txt [...] A A A Binary file testfile.txt matches Exit code of grep: 0 I also found this bug in older grep versions (e.g. Ubuntu 14.04; grep 2.16). FreeBSD's version of grep (tested with 2.5.1-FreeBSD under FreeBSD 10.3-RELEASE-p4) does not show the bug: #./null-bug-testcase.txt [...] A A A A ... the end Exit code of grep: 0 Regards, Björn
