3 ms·

To my experience (and if only the filename is needed) the "-1" option helps saving some time too. Be aware that output from ls without options differ, if redire

To my experience (and if only the filename is needed) the "-1" option helps saving some time too. Be aware that output from ls without options differ, if redirected. time (real user sys) in seconds with 1e6 files in a xfs filesystem. Directory used 27 MB space. ls -l > /dev/null : 49.12 23.90 13.47 ls -lU > /dev/null : 46.62 33.11 8.01 ls > /dev/null : 6.36 1.97 3.63 ls -1 > /dev/null : 2.49 1.83 0.36 ls -1U > /dev/null : 0.31 0.18 0.08 (find) : 0.77 0.49 0.19 and for 1e6 files in an ext4 filesystem. Directory used 23 MB space. (but as i had no ext4 fs with one million free inodes on a loop device) ls -l > /dev/null : 51.39 34.02 11.39 ls -lU > /dev/null : 47.39 30.72 11.09 ls > /dev/null : 4.83 3.56 0.65 ls -1 > /dev/null : 4.46 3.45 0.50 ls -1U > /dev/null : 0.51 0.18 0.26 (find) : 1.29 0.76 0.36

jeffbee 3y ago
Good info. But isn't `-1` implicit when the output is a pipe?
- sllabres 3y ago
  Good reply, you are right. I have even written ("Be aware that output from ls without options differ, if redirected") that it is so but was somewhat fooled by my experiment and the different timings for "ls" and "ls -1" when using XFS. Of course I was not able to reproduce this difference and assume that I did work on the system and it was not idle. I have repeated the the tests, on another mostly idle system. (Therefor the timing is not comparable to the first test). This time both filesystems live in a loop device and the benchmarks were run with hyperfine (3 warmup loops, 3 measurements each). XFS ls -l >/dev/null Time (mean ± σ): 5.890 s ± 0.394 s [User: 1.096 s, System: 3.491 s] ls -lU >/dev/null Time (mean ± σ): 2.254 s ± 0.386 s [User: 0.648 s, System: 1.602 s] ls >/dev/null Time (mean ± σ): 542.7 ms ± 4.4 ms [User: 443.8 ms, System: 98.7 ms] ls -1 >/dev/null Time (mean ± σ): 534.4 ms ± 2.3 ms [User: 450.1 ms, System: 84.1 ms] ls -1U >/dev/null Time (mean ± σ): 115.8 ms ± 1.8 ms [User: 80.9 ms, System: 34.6 ms] ls -U >/dev/null Time (mean ± σ): 121.0 ms ± 14.6 ms [User: 80.9 ms, System: 40.0 ms] find >/dev/null Time (mean ± σ): 225.0 ms ± 16.2 ms [User: 150.1 ms, System: 74.7 ms] EXT4 ls -l >/dev/null Time (mean ± σ): 10.493 s ± 0.392 s [User: 2.495 s, System: 5.032 s] ls -lU >/dev/null Time (mean ± σ): 8.395 s ± 0.157 s [User: 0.735 s, System: 5.049 s] ls >/dev/null Time (mean ± σ): 1.966 s ± 0.010 s [User: 1.760 s, System: 0.202 s] ls -1 >/dev/null Time (mean ± σ): 2.014 s ± 0.032 s [User: 1.798 s, System: 0.216 s] ls -1U >/dev/null Time (mean ± σ): 221.4 ms ± 1.3 ms [User: 83.7 ms, System: 137.6 ms] ls -U >/dev/null Time (mean ± σ): 222.5 ms ± 2.0 ms [User: 78.9 ms, System: 143.6 ms] find >/dev/null Time (mean ± σ): 531.0 ms ± 4.0 ms [User: 377.3 ms, System: 153.7 ms]

jeffbee 3y ago

Good info. But isn't `-1` implicit when the output is a pipe?

sllabres 3y ago
Good reply, you are right. I have even written ("Be aware that output from ls without options differ, if redirected") that it is so but was somewhat fooled by my experiment and the different timings for "ls" and "ls -1" when using XFS. Of course I was not able to reproduce this difference and assume that I did work on the system and it was not idle. I have repeated the the tests, on another mostly idle system. (Therefor the timing is not comparable to the first test). This time both filesystems live in a loop device and the benchmarks were run with hyperfine (3 warmup loops, 3 measurements each). XFS ls -l >/dev/null Time (mean ± σ): 5.890 s ± 0.394 s [User: 1.096 s, System: 3.491 s] ls -lU >/dev/null Time (mean ± σ): 2.254 s ± 0.386 s [User: 0.648 s, System: 1.602 s] ls >/dev/null Time (mean ± σ): 542.7 ms ± 4.4 ms [User: 443.8 ms, System: 98.7 ms] ls -1 >/dev/null Time (mean ± σ): 534.4 ms ± 2.3 ms [User: 450.1 ms, System: 84.1 ms] ls -1U >/dev/null Time (mean ± σ): 115.8 ms ± 1.8 ms [User: 80.9 ms, System: 34.6 ms] ls -U >/dev/null Time (mean ± σ): 121.0 ms ± 14.6 ms [User: 80.9 ms, System: 40.0 ms] find >/dev/null Time (mean ± σ): 225.0 ms ± 16.2 ms [User: 150.1 ms, System: 74.7 ms] EXT4 ls -l >/dev/null Time (mean ± σ): 10.493 s ± 0.392 s [User: 2.495 s, System: 5.032 s] ls -lU >/dev/null Time (mean ± σ): 8.395 s ± 0.157 s [User: 0.735 s, System: 5.049 s] ls >/dev/null Time (mean ± σ): 1.966 s ± 0.010 s [User: 1.760 s, System: 0.202 s] ls -1 >/dev/null Time (mean ± σ): 2.014 s ± 0.032 s [User: 1.798 s, System: 0.216 s] ls -1U >/dev/null Time (mean ± σ): 221.4 ms ± 1.3 ms [User: 83.7 ms, System: 137.6 ms] ls -U >/dev/null Time (mean ± σ): 222.5 ms ± 2.0 ms [User: 78.9 ms, System: 143.6 ms] find >/dev/null Time (mean ± σ): 531.0 ms ± 4.0 ms [User: 377.3 ms, System: 153.7 ms]