Determine free space available on a USB flash drive in C (linux)
I would like to figure out the available free space on a USB flash drive in a C program in Linux. I have earlier used system("df -h /dev/sda1") to figure it out but using system command in a Linux C application is causing some timing issues. Hence need to know how to determine available free space using any kind of system call.
linux usb usb-drive c system-calls
edited 3 hours ago
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asked 3 hours ago
OpenSourceEnthusiastOpenSourceEnthusiast
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I would like to figure out the available free space on a USB flash drive in a C program in Linux. I have earlier used system("df -h /dev/sda1") to figure it out but using system command in a Linux C application is causing some timing issues. Hence need to know how to determine available free space using any kind of system call.
linux usb usb-drive c system-calls
edited 3 hours ago
PRY
2,01931025
asked 3 hours ago
OpenSourceEnthusiastOpenSourceEnthusiast
335
add a comment |
I would like to figure out the available free space on a USB flash drive in a C program in Linux. I have earlier used system("df -h /dev/sda1") to figure it out but using system command in a Linux C application is causing some timing issues. Hence need to know how to determine available free space using any kind of system call.
linux usb usb-drive c system-calls
edited 3 hours ago
PRY
2,01931025
asked 3 hours ago
OpenSourceEnthusiastOpenSourceEnthusiast
335
I would like to figure out the available free space on a USB flash drive in a C program in Linux. I have earlier used system("df -h /dev/sda1") to figure it out but using system command in a Linux C application is causing some timing issues. Hence need to know how to determine available free space using any kind of system call.
linux usb usb-drive c system-calls
linux usb usb-drive c system-calls
edited 3 hours ago
PRY
2,01931025
asked 3 hours ago
OpenSourceEnthusiastOpenSourceEnthusiast
335
edited 3 hours ago
PRY
2,01931025
asked 3 hours ago
OpenSourceEnthusiastOpenSourceEnthusiast
335
edited 3 hours ago
PRY
2,01931025
edited 3 hours ago
PRY
2,01931025
edited 3 hours ago
PRY
2,01931025
2,01931025
asked 3 hours ago
OpenSourceEnthusiastOpenSourceEnthusiast
335
asked 3 hours ago
OpenSourceEnthusiastOpenSourceEnthusiast
335
asked 3 hours ago
OpenSourceEnthusiastOpenSourceEnthusiast
335
335
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
For a mounted USB flash drive, you can do this via statvfs(3) function, where you need to provide path to the mountpoint, and you basically have a small version of df (which also btw only operates on mounted filesystems):
$ cat fs_usage.c
#include <stdio.h>
#include <sys/statvfs.h>
int main(int argc, char **argv){
struct statvfs fs_usage;
statvfs(argv[1],&fs_usage);
printf("%s:%f bytes available, %f bytes usedn",argv[1],
fs_usage.f_frsize*(double)fs_usage.f_bavail,
fs_usage.f_frsize * (double)(fs_usage.f_blocks - fs_usage.f_bfree));
return 0;
}
$ gcc fs_usage.c -o fs_usage
$ df -B 1 /mnt/ubuntu
Filesystem 1B-blocks Used Available Use% Mounted on
/dev/sdb1 118013599744 105134329856 6860865536 94% /mnt/ubuntu
$ ./fs_usage /mnt/ubuntu/
/mnt/ubuntu/:6860865536.000000 bytes available, 105134329856.000000 bytes used
Note also that statvfs() takes const char *path as one of the parameters, and that can be pathname of any file within the filesystem, e.g. /dev/sda7 will return usage of /dev filesystem ( because it is in fact one of virtual filesystems ), and not the sda7 partition of a device.
Note that I am using f_frsize here, which is equivalent to f_bsize, however in some filesystems fragment size may be smaller than block size. See https://unix.stackexchange.com/a/463370/85039 for details
answered 3 hours ago
Sergiy KolodyazhnyySergiy Kolodyazhnyy
10.1k32660
statvfs(3) is not a system call; it's a library function implemented on top of the statfs(2) (without v) system call.
– Uncle Billy
3 hours ago
@UncleBilly Thanks, corrected
– Sergiy Kolodyazhnyy
3 hours ago
When I ran the above code, I see some precision loss as compared to the values reported by df command. For instance, df reports available space as 21M and the above code reports available space as 20M. How do we get very accurate values for available space (till . precision)
– OpenSourceEnthusiast
3 hours ago
1
maybe you should mention that statvfs it will work on any file contained in the fs, not just the mount point --statvfs("/dev/sda7", &vfs)will return info about the devtmpfs file system, not about the filesystem contained in/dev/sda7.
– Uncle Billy
3 hours ago
@OpenSourceEnthusiast Did you rundfwith-B 1or without ? By default GNUdfdefaults to blocks of 1024 bytes, but with-B 1block size is set to 1 byte.
– Sergiy Kolodyazhnyy
2 hours ago
|
show 6 more comments
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1 Answer
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For a mounted USB flash drive, you can do this via statvfs(3) function, where you need to provide path to the mountpoint, and you basically have a small version of df (which also btw only operates on mounted filesystems):
$ cat fs_usage.c
#include <stdio.h>
#include <sys/statvfs.h>
int main(int argc, char **argv){
struct statvfs fs_usage;
statvfs(argv[1],&fs_usage);
printf("%s:%f bytes available, %f bytes usedn",argv[1],
fs_usage.f_frsize*(double)fs_usage.f_bavail,
fs_usage.f_frsize * (double)(fs_usage.f_blocks - fs_usage.f_bfree));
return 0;
}
$ gcc fs_usage.c -o fs_usage
$ df -B 1 /mnt/ubuntu
Filesystem 1B-blocks Used Available Use% Mounted on
/dev/sdb1 118013599744 105134329856 6860865536 94% /mnt/ubuntu
$ ./fs_usage /mnt/ubuntu/
/mnt/ubuntu/:6860865536.000000 bytes available, 105134329856.000000 bytes used
Note also that statvfs() takes const char *path as one of the parameters, and that can be pathname of any file within the filesystem, e.g. /dev/sda7 will return usage of /dev filesystem ( because it is in fact one of virtual filesystems ), and not the sda7 partition of a device.
Note that I am using f_frsize here, which is equivalent to f_bsize, however in some filesystems fragment size may be smaller than block size. See https://unix.stackexchange.com/a/463370/85039 for details
answered 3 hours ago
Sergiy KolodyazhnyySergiy Kolodyazhnyy
10.1k32660
statvfs(3) is not a system call; it's a library function implemented on top of the statfs(2) (without v) system call.
– Uncle Billy
3 hours ago
@UncleBilly Thanks, corrected
– Sergiy Kolodyazhnyy
3 hours ago
When I ran the above code, I see some precision loss as compared to the values reported by df command. For instance, df reports available space as 21M and the above code reports available space as 20M. How do we get very accurate values for available space (till . precision)
– OpenSourceEnthusiast
3 hours ago
1
maybe you should mention that statvfs it will work on any file contained in the fs, not just the mount point --statvfs("/dev/sda7", &vfs)will return info about the devtmpfs file system, not about the filesystem contained in/dev/sda7.
– Uncle Billy
3 hours ago
@OpenSourceEnthusiast Did you rundfwith-B 1or without ? By default GNUdfdefaults to blocks of 1024 bytes, but with-B 1block size is set to 1 byte.
– Sergiy Kolodyazhnyy
2 hours ago
|
show 6 more comments
For a mounted USB flash drive, you can do this via statvfs(3) function, where you need to provide path to the mountpoint, and you basically have a small version of df (which also btw only operates on mounted filesystems):
$ cat fs_usage.c
#include <stdio.h>
#include <sys/statvfs.h>
int main(int argc, char **argv){
struct statvfs fs_usage;
statvfs(argv[1],&fs_usage);
printf("%s:%f bytes available, %f bytes usedn",argv[1],
fs_usage.f_frsize*(double)fs_usage.f_bavail,
fs_usage.f_frsize * (double)(fs_usage.f_blocks - fs_usage.f_bfree));
return 0;
}
$ gcc fs_usage.c -o fs_usage
$ df -B 1 /mnt/ubuntu
Filesystem 1B-blocks Used Available Use% Mounted on
/dev/sdb1 118013599744 105134329856 6860865536 94% /mnt/ubuntu
$ ./fs_usage /mnt/ubuntu/
/mnt/ubuntu/:6860865536.000000 bytes available, 105134329856.000000 bytes used
Note also that statvfs() takes const char *path as one of the parameters, and that can be pathname of any file within the filesystem, e.g. /dev/sda7 will return usage of /dev filesystem ( because it is in fact one of virtual filesystems ), and not the sda7 partition of a device.
Note that I am using f_frsize here, which is equivalent to f_bsize, however in some filesystems fragment size may be smaller than block size. See https://unix.stackexchange.com/a/463370/85039 for details
answered 3 hours ago
Sergiy KolodyazhnyySergiy Kolodyazhnyy
10.1k32660
statvfs(3) is not a system call; it's a library function implemented on top of the statfs(2) (without v) system call.
– Uncle Billy
3 hours ago
@UncleBilly Thanks, corrected
– Sergiy Kolodyazhnyy
3 hours ago
When I ran the above code, I see some precision loss as compared to the values reported by df command. For instance, df reports available space as 21M and the above code reports available space as 20M. How do we get very accurate values for available space (till . precision)
– OpenSourceEnthusiast
3 hours ago
1
maybe you should mention that statvfs it will work on any file contained in the fs, not just the mount point --statvfs("/dev/sda7", &vfs)will return info about the devtmpfs file system, not about the filesystem contained in/dev/sda7.
– Uncle Billy
3 hours ago
@OpenSourceEnthusiast Did you rundfwith-B 1or without ? By default GNUdfdefaults to blocks of 1024 bytes, but with-B 1block size is set to 1 byte.
– Sergiy Kolodyazhnyy
2 hours ago
|
show 6 more comments
For a mounted USB flash drive, you can do this via statvfs(3) function, where you need to provide path to the mountpoint, and you basically have a small version of df (which also btw only operates on mounted filesystems):
$ cat fs_usage.c
#include <stdio.h>
#include <sys/statvfs.h>
int main(int argc, char **argv){
struct statvfs fs_usage;
statvfs(argv[1],&fs_usage);
printf("%s:%f bytes available, %f bytes usedn",argv[1],
fs_usage.f_frsize*(double)fs_usage.f_bavail,
fs_usage.f_frsize * (double)(fs_usage.f_blocks - fs_usage.f_bfree));
return 0;
}
$ gcc fs_usage.c -o fs_usage
$ df -B 1 /mnt/ubuntu
Filesystem 1B-blocks Used Available Use% Mounted on
/dev/sdb1 118013599744 105134329856 6860865536 94% /mnt/ubuntu
$ ./fs_usage /mnt/ubuntu/
/mnt/ubuntu/:6860865536.000000 bytes available, 105134329856.000000 bytes used
Note also that statvfs() takes const char *path as one of the parameters, and that can be pathname of any file within the filesystem, e.g. /dev/sda7 will return usage of /dev filesystem ( because it is in fact one of virtual filesystems ), and not the sda7 partition of a device.
Note that I am using f_frsize here, which is equivalent to f_bsize, however in some filesystems fragment size may be smaller than block size. See https://unix.stackexchange.com/a/463370/85039 for details
answered 3 hours ago
Sergiy KolodyazhnyySergiy Kolodyazhnyy
10.1k32660
For a mounted USB flash drive, you can do this via statvfs(3) function, where you need to provide path to the mountpoint, and you basically have a small version of df (which also btw only operates on mounted filesystems):
$ cat fs_usage.c
#include <stdio.h>
#include <sys/statvfs.h>
int main(int argc, char **argv){
struct statvfs fs_usage;
statvfs(argv[1],&fs_usage);
printf("%s:%f bytes available, %f bytes usedn",argv[1],
fs_usage.f_frsize*(double)fs_usage.f_bavail,
fs_usage.f_frsize * (double)(fs_usage.f_blocks - fs_usage.f_bfree));
return 0;
}
$ gcc fs_usage.c -o fs_usage
$ df -B 1 /mnt/ubuntu
Filesystem 1B-blocks Used Available Use% Mounted on
/dev/sdb1 118013599744 105134329856 6860865536 94% /mnt/ubuntu
$ ./fs_usage /mnt/ubuntu/
/mnt/ubuntu/:6860865536.000000 bytes available, 105134329856.000000 bytes used
Note also that statvfs() takes const char *path as one of the parameters, and that can be pathname of any file within the filesystem, e.g. /dev/sda7 will return usage of /dev filesystem ( because it is in fact one of virtual filesystems ), and not the sda7 partition of a device.
Note that I am using f_frsize here, which is equivalent to f_bsize, however in some filesystems fragment size may be smaller than block size. See https://unix.stackexchange.com/a/463370/85039 for details
answered 3 hours ago
Sergiy KolodyazhnyySergiy Kolodyazhnyy
10.1k32660
edited 53 mins ago
answered 3 hours ago
Sergiy KolodyazhnyySergiy Kolodyazhnyy
10.1k32660
answered 3 hours ago
Sergiy KolodyazhnyySergiy Kolodyazhnyy
10.1k32660
answered 3 hours ago
Sergiy KolodyazhnyySergiy Kolodyazhnyy
10.1k32660
10.1k32660
statvfs(3) is not a system call; it's a library function implemented on top of the statfs(2) (without v) system call.
– Uncle Billy
3 hours ago
@UncleBilly Thanks, corrected
– Sergiy Kolodyazhnyy
3 hours ago
When I ran the above code, I see some precision loss as compared to the values reported by df command. For instance, df reports available space as 21M and the above code reports available space as 20M. How do we get very accurate values for available space (till . precision)
– OpenSourceEnthusiast
3 hours ago
1
maybe you should mention that statvfs it will work on any file contained in the fs, not just the mount point --statvfs("/dev/sda7", &vfs)will return info about the devtmpfs file system, not about the filesystem contained in/dev/sda7.
– Uncle Billy
3 hours ago
@OpenSourceEnthusiast Did you rundfwith-B 1or without ? By default GNUdfdefaults to blocks of 1024 bytes, but with-B 1block size is set to 1 byte.
– Sergiy Kolodyazhnyy
2 hours ago
|
show 6 more comments
statvfs(3) is not a system call; it's a library function implemented on top of the statfs(2) (without v) system call.
– Uncle Billy
3 hours ago
@UncleBilly Thanks, corrected
– Sergiy Kolodyazhnyy
3 hours ago
When I ran the above code, I see some precision loss as compared to the values reported by df command. For instance, df reports available space as 21M and the above code reports available space as 20M. How do we get very accurate values for available space (till . precision)
– OpenSourceEnthusiast
3 hours ago
1
maybe you should mention that statvfs it will work on any file contained in the fs, not just the mount point --statvfs("/dev/sda7", &vfs)will return info about the devtmpfs file system, not about the filesystem contained in/dev/sda7.
– Uncle Billy
3 hours ago
@OpenSourceEnthusiast Did you rundfwith-B 1or without ? By default GNUdfdefaults to blocks of 1024 bytes, but with-B 1block size is set to 1 byte.
– Sergiy Kolodyazhnyy
2 hours ago
statvfs(3) is not a system call; it's a library function implemented on top of the statfs(2) (without v) system call.
– Uncle Billy
3 hours ago
statvfs(3) is not a system call; it's a library function implemented on top of the statfs(2) (without v) system call.
– Uncle Billy
3 hours ago
@UncleBilly Thanks, corrected
– Sergiy Kolodyazhnyy
3 hours ago
@UncleBilly Thanks, corrected
– Sergiy Kolodyazhnyy
3 hours ago
When I ran the above code, I see some precision loss as compared to the values reported by df command. For instance, df reports available space as 21M and the above code reports available space as 20M. How do we get very accurate values for available space (till . precision)
– OpenSourceEnthusiast
3 hours ago
When I ran the above code, I see some precision loss as compared to the values reported by df command. For instance, df reports available space as 21M and the above code reports available space as 20M. How do we get very accurate values for available space (till . precision)
– OpenSourceEnthusiast
3 hours ago
1
1
maybe you should mention that statvfs it will work on any file contained in the fs, not just the mount point --
statvfs("/dev/sda7", &vfs) will return info about the devtmpfs file system, not about the filesystem contained in /dev/sda7.– Uncle Billy
3 hours ago
maybe you should mention that statvfs it will work on any file contained in the fs, not just the mount point --
statvfs("/dev/sda7", &vfs) will return info about the devtmpfs file system, not about the filesystem contained in /dev/sda7.– Uncle Billy
3 hours ago
@OpenSourceEnthusiast Did you run
df with -B 1 or without ? By default GNU df defaults to blocks of 1024 bytes, but with -B 1 block size is set to 1 byte.– Sergiy Kolodyazhnyy
2 hours ago
@OpenSourceEnthusiast Did you run
df with -B 1 or without ? By default GNU df defaults to blocks of 1024 bytes, but with -B 1 block size is set to 1 byte.– Sergiy Kolodyazhnyy
2 hours ago
|
show 6 more comments
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