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NAME |SYNOPSIS |DESCRIPTION |TEXTUAL REPRESENTATION |RETURN VALUE |CONFORMING TO |EXAMPLE |SEE ALSO |COLOPHON | |
CAP_FROM_TEXT(3) Linux Programmer's ManualCAP_FROM_TEXT(3)cap_from_text, cap_to_text, cap_to_name, cap_from_name - capability state textual representation translation
#include <sys/capability.h> cap_t cap_from_text(const char *buf_p); char *cap_to_text(cap_t caps, ssize_t *len_p); int cap_from_name(const char *name, cap_value_t *cap_p); char *cap_to_name(cap_value_t cap); Link with-lcap.
These functions translate a capability state between an internal representation and a textual one. The internal representation is managed by the capability functions in working storage. The textual representation is a structured, human-readable string suitable for display.cap_from_text() allocates and initializes a capability state in working storage. It then sets the contents of this newly created capability state to the state represented by a human-readable, nul-terminated character string pointed to bybuf_p. It returns a pointer to the newly created capability state. When the capability state in working storage is no longer required, the caller should free any releasable memory by callingcap_free() withcap_t as an argument. The function returns an error if it cannot parse the contents of the string pointed to bybuf_p or does not recognize anycapability_name or flag character as valid. The function also returns an error if any flag is both set and cleared within a single clause.cap_to_text() converts the capability state in working storage identified bycaps into a nul-terminated human-readable string. This function allocates any memory necessary to contain the string, and returns a pointer to the string. If the pointerlen_p is not NULL, the function shall also return the full length of the string (not including the nul terminator) in the location pointed to bylen_p. The capability state in working storage, identified bycaps, is completely represented in the character string. When the capability state in working storage is no longer required, the caller should free any releasable memory by callingcap_free() with the returned string pointer as an argument.cap_from_name() converts a text representation of a capability, such as "cap_chown", to its numerical representation (CAP_CHOWN=0), writing the decoded value into*cap_p. Ifcap_p is NULL no result is written, but the return code of the function indicates whether or not the specified capability can be represented by the library.cap_to_name() converts a capability index value,cap, to a libcap- allocated textual string. This string should be deallocated withcap_free().
The text format is described in thecap_text_formats(7) man page.
cap_from_text(),cap_to_text() andcap_to_name() return a non-NULL value on success, and NULL on failure.cap_from_name() returns 0 for success, and -1 on failure (unknown capability). On failure,errno is set toEINVAL, orENOMEM.
cap_from_text() andcap_to_text() are specified by the withdrawn POSIX.1e draft specification.cap_from_name() andcap_to_name() are Linux extensions.
The example program below demonstrates the use ofcap_from_text() andcap_to_text(). The following shell session shows some example runs: $ ./a.out "cap_chown=p cap_chown+e" caps_to_text() returned "cap_chown=ep" $ ./a.out "all=pe cap_chown-e cap_kill-pe" caps_to_text() returned "=ep cap_chown-e cap_kill-ep" The source code of the program is as follows: #include <stdlib.h> #include <stdio.h> #include <sys/capability.h> #define handle_error(msg) \ do { perror(msg); exit(EXIT_FAILURE); } while (0) int main(int argc, char *argv[]) { cap_t caps; char *txt_caps; if (argc != 2) { fprintf(stderr, "%s <textual-cap-set>\n", argv[0]); exit(EXIT_FAILURE); } caps = cap_from_text(argv[1]); if (caps == NULL) handle_error("cap_from_text"); txt_caps = cap_to_text(caps, NULL); if (txt_caps == NULL) handle_error("cap_to_text"); printf("caps_to_text() returned \"%s\"\n", txt_caps); if (cap_free(txt_caps) != 0 || cap_free(caps) != 0) handle_error("cap_free"); exit(EXIT_SUCCESS); }libcap(3),cap_clear(3),cap_copy_ext(3),cap_get_file(3),cap_get_proc(3),cap_init(3),cap_text_formats(7),capabilities(7)
This page is part of thelibcap (capabilities commands and library) project. Information about the project can be found at ⟨https://git.kernel.org/pub/scm/libs/libcap/libcap.git/⟩. If you have a bug report for this manual page, send it to morgan@kernel.org (please put "libcap" in the Subject line). This page was obtained from the project's upstream Git repository ⟨https://git.kernel.org/pub/scm/libs/libcap/libcap.git/⟩ on 2025-08-11. (At that time, the date of the most recent commit that was found in the repository was 2025-08-10.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which isnot part of the original manual page), send a mail to man-pages@man7.org 2025-03-19CAP_FROM_TEXT(3)Pages that refer to this page:capsh(1), cap_clear(3), cap_copy_ext(3), cap_get_file(3), cap_get_proc(3), cap_init(3), libcap(3), org.freedesktop.systemd1(5), systemd-system.conf(5), capabilities(7), cap_text_formats(7), captree(8), getcap(8), getpcaps(8), setcap(8)
HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH. | |