Strace
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System Trace is a tool for hackers.
Say you have some python application such as Reposurgeon that you need to understand better. You can attach strace to the pid of the running application to see the underlying system calls being made.
sudo strace -f -s128 -e trace=open -p$(ps -o lwp= -LC python2 | tail -1)
# -f follow child processes
# -s string width
# -e set which calls you want to see. Using trace=open is like sudo lsof -ad3-999 -c python2
write(1, "reposurgeon: r10952 copynode filemap is <PathMap: branches/784.919Merge/diag/Makefile branches/784.919Merge/diag/changelog branc"..., 1024) = 1024 write(1, "/cmts.cmd.h branches/784.919Merge/diag/cli/commands/cmts_dsg.cmd.h branches/784.919Merge/diag/cli/commands/copy.cmd branches/784"..., 412067840) = 412067840 write(1, "c/zebos/rip/rip_distance.c trunk/linux/src/zebos/rip/rip_distance.h trunk/linux/src/zebos/rip/rip_host.h trunk/linux/src/zebos/r"..., 888) = 888 munmap(0x7f888d31c000, 412069888) = 0 munmap(0x7f885c126000, 412069888) = 0 mmap(NULL, 412069888, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f888d31d000 mmap(NULL, 412069888, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f8874a22000 munmap(0x7f888d31d000, 412069888) = 0 mmap(NULL, 412073984, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f885c126000 munmap(0x7f8874a22000, 412069888) = 0 mremap(0x7f885c126000, 412073984, 412069888, MREMAP_MAYMOVE) = 0x7f885c126000 mmap(NULL, 412073984, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f888d31c000 mremap(0x7f888d31c000, 412073984, 412069888, MREMAP_MAYMOVE) = 0x7f888d31c000 write(1, "reposurgeon: r10952 copynode filemap is <PathMap: branches/784.919Merge/diag/Makefile branches/784.919Merge/diag/changelog branc"..., 1024) = 1024 write(1, "/cmts.cmd.h branches/784.919Merge/diag/cli/commands/cmts_dsg.cmd.h branches/784.919Merge/diag/cli/commands/copy.cmd branches/784"..., 412067840) = 412067840 write(1, "c/zebos/rip/rip_distance.c trunk/linux/src/zebos/rip/rip_distance.h trunk/linux/src/zebos/rip/rip_host.h trunk/linux/src/zebos/r"..., 888) = 888 munmap(0x7f888d31c000, 412069888) = 0 munmap(0x7f885c126000, 412069888) = 0 mmap(NULL, 412069888, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f888d31d000 mmap(NULL, 412069888, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f8874a22000 munmap(0x7f888d31d000, 412069888) = 0 mmap(NULL, 412073984, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f885c126000 munmap(0x7f8874a22000, 412069888) = 0 mremap(0x7f885c126000, 412073984, 412069888, MREMAP_MAYMOVE) = 0x7f885c126000 mmap(NULL, 412073984, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f888d31c000 mremap(0x7f888d31c000, 412073984, 412069888, MREMAP_MAYMOVE) = 0x7f888d31c000 write(1, "reposurgeon: r10952 copynode filemap is <PathMap: branches/784.919Merge/diag/Makefile branches/784.919Merge/diag/changelog branc"..., 1024) = 1024 write(1, "/cmts.cmd.h branches/784.919Merge/diag/cli/commands/cmts_dsg.cmd.h branches/784.919Merge/diag/cli/commands/copy.cmd branches/784"..., 412067840) = 412067840 write(1, "c/zebos/rip/rip_distance.c trunk/linux/src/zebos/rip/rip_distance.h trunk/linux/src/zebos/rip/rip_host.h trunk/linux/src/zebos/r"..., 888) = 888 munmap(0x7f888d31c000, 412069888) = 0 munmap(0x7f885c126000, 412069888) = 0 mmap(NULL, 412069888, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f888d31d000 mmap(NULL, 412069888, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f8874a22000 munmap(0x7f888d31d000, 412069888) = 0 mmap(NULL, 412073984, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f885c126000 munmap(0x7f8874a22000, 412069888) = 0 mremap(0x7f885c126000, 412073984, 412069888, MREMAP_MAYMOVE) = 0x7f885c126000 mmap(NULL, 412073984, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f888d31c000 mremap(0x7f888d31c000, 412073984, 412069888, MREMAP_MAYMOVE) = 0x7f888d31c000 write(1, "reposurgeon: r10952 copynode filemap is <PathMap: branches/784.919Merge/diag/Makefile branches/784.919Merge/diag/changelog branc"..., 1024) = 1024 write(1, "/cmts.cmd.h branches/784.919Merge/diag/cli/commands/cmts_dsg.cmd.h branches/784.919Merge/diag/cli/commands/copy.cmd branches/784"..., 412067840) = 412067840 write(1, "c/zebos/rip/rip_distance.c trunk/linux/src/zebos/rip/rip_distance.h trunk/linux/src/zebos/rip/rip_host.h trunk/linux/src/zebos/r"..., 888) = 888 munmap(0x7f888d31c000, 412069888) = 0 munmap(0x7f885c126000, 412069888) = 0
