Renzo at 10:56, 13 November 2025

2025-11-13T10:56:24Z

Renzo: Created page with "

 tutte queste syscall restituiscono il valore 0 se l'operazione ha                                                                                                       s..."

2025-11-11T16:59:17Z

Created page with "<pre> tutte queste syscall restituiscono il valore 0 se l'operazione ha s..."

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<pre>
tutte queste syscall restituiscono il valore 0 se l'operazione ha
successo o -1 in caso di errore (il tipo di errore lo si legge nella
"variabile" errno).
Le system call indicate con (R!) possono essere eseguite solo da
utenti privilegiati (root)

// change working directory
chdir("/home/user") cd /home/user

// create directory
mkdir("/tmp/mydir", 0755) mkdir -m 755 /tmp/mydir

// remove (empty) directory
rmdir("/tmp/olddir") rmdir /tmp/olddir

// create (hard) link:
// add one more name to a file
link("vecchio", "/tmp/nuovo") ln vecchio /tmp/nuovo

// create symbolic link
link("vecchio", "/tmp/nuovolink") ln -s vecchio /tmp/nuovolink

// delete one name of a file,
// removed it when it has no more names
unlink("/tmp/dacancellare") rm /tmp/dacancellare

// rename a file (atomically!)
rename("vecchionome", "nuovonome") rename vecchionome nuovonome

// get file info (show i-node data)
struct stat buf;
stat("/tmp/symlink", &buf) stat -f /tmp/symlink
/* le info vengono scritte in buf */

// get file info
// (do not follow symbolic links)
struct stat buf;
lstat("/tmp/symlink", &buf) stat /tmp/symlink
/* le info vengono scritte in buf */

// change file permissions
chmod("/tmp/miofile", 0750) chmod 0750 /tmp/miofile

// change file ownership (R!)
chown("/tmp/miofile", 1000, 1000) chown 1000:1000 /tmp/miofile
/* il primo 1000 è l'user-id (uid),
il secondo è il group-id (gid) */

// change file ownership (R!)
// (do not follow symbolic links)
lchown("/tmp/miofile", 1000, 1000) chown -P 1000:1000 /tmp/miofile
/* il primo 1000 è l'user-id (uid),
il secondo è il group-id (gid) */

// truncate the contents of a file to a specific length
truncate("/tmp/file", 420) truncate -s 420 /tmp/file

// get info of a mounted file system
struct statfs buf;
statfs("/", &buf) statfs /
/* le info vengono scritte in buf */

// change root directory (R!)
chroot("/tmp/newroot") chroot /tmp/newroot

// mount a filesystem (R!)
mount("/dev/hda0", "/mnt", "ext4", MS_RDONLY, "")
mount -o ro -t ext4 /dev/hda0 /mnt

// umount a filesystem (R!)
umount("/mnt") umount /mnt

// create a special file
mknod("tmp/myfifo", S_IFIFO | 0770, 0) mkfifo -m 770 /tmp/myfifo

// create a special file (device) (R!)
// major number = 1, minor number = 7
mknod("/tmp/mydev", S_IFCHR | 0660, mknod -m 660 /tmp/mydev c 1 7
makedev(1, 7));

// change access/modification time
struct utimbuf ut = {time(NULL), time(NULL)};
utime("/tmp/myfile", &ut);
touch /tm/myfile

------------
// get the urrent working directory
// the glibc wrapper function returns
// a string
#include <linux/limits.h> readlink /tmp/symlink
...
char path[PATH_MAX]; pwd
if (getcwd(path, PATH_MAX) == NULL)
/* error management */

// read the value of a symbolic link
#include <linux/limits.h> readlink /tmp/symlink
...
char path[PATH_MAX];
ssize_t pathlen =
readlink("/tmp/symlink", path, PATH_MAX);
if (pathlen == -1) /* error management */ ;
else
path[pathlen] = 0;

// test if a file exists, or is readable/writable/executable
// the return value of access is 0=true (success), -1=false (failure)
// the exit value of the test command is 0=true, 1=false

access("/tmp/file", F_OK) ↔ test -e /tmp/file
access("/tmp/file", R_OK) ↔ test -r /tmp/file
access("/tmp/file", W_OK) ↔ test -w /tmp/file
access("/tmp/file", X_OK) ↔ test -x /tmp/file

</pre>

Syscall per file system: equivalenza comandi - Revision history

Renzo at 10:56, 13 November 2025

Renzo: Created page with "
tutte queste syscall restituiscono il valore 0 se l'operazione ha s..."

@@ Line 20: / Line 20: @@
 // create symbolic link
-link("vecchio", "/tmp/nuovolink")        ln -s vecchio /tmp/nuovolink
+symlink("vecchio", "/tmp/nuovolink")        ln -s vecchio /tmp/nuovolink
 // delete one name of a file,